Arne Vodder for H. P. Hansen's Rosewood Desk circa 1965  

You can probably find screws somewhere that are just as good as vintage.  Just look or ask for flat head wood screws.  They can be hard to find, and don't use phillips head.
Did Arne Vodder design anything for H.P. Hansen?  I've never heard of that connection before, and I've certainly never seen any documentation on it.  Is this right??

Thank you Leif. I did find the traditional wood screws, but the plating is zinc plate. I believe the vintage screws have a different plating, not as bright of a finish. I'm still looiking for the drawer guide, but no luck thus far.
Yes, it's a rare connection between Arne Vodder and H.P. Hansen's Mobelindustri, Denmark. However, I came across this when researching the desk manufacturer. I've located the exact same desk sold through Refine Modern and a couple other places specializing in mid-century modern furniture.
 

I don't know the people at Refine Modern, but I would want more than their say so to believe it is an Arne Vodder design.  Have you asked them what they based the credit on?
And that is an interesting point about the zinc plating (galvanization).  I know that zinc gets very dull with a bit of age to just about the color of raw steel.  So I am not sure if wood screws of 60 years past were not galvanized, or if the zinc has just dulled with oxidation.   I suspect they were zinc plated back then as well.  
Also, bear in mind that in certain applications brass screws were specifically used because they would not cause blackening through interaction with the tannins in the wood.

Hmmm... looks an awful lot like Phillips screws in that last pic! Furniture restorers will often keep old hardware and fasteners for just these occasions. You might get lucky asking around locally if strict originality is that important. Otherwise, just use new until you can find vintage. Lathe-cut screws are far superior, I agree, and getting pretty scarce.
Gorgeous desk, though. Would you have a photo or better description of the plastic drawer guide you need?

Tktoo: well spotted. Those are definitely replacement screws. And I think you are indicating you know the difference between vintage screws and contemporary(?).  I am curious tell me more, please.

i've replaced the Phillips screws with the traditional slotted wood screws; that's an old image. This desk belong to my father-in-law who is from Copenhagen, Denmark. He ordered it and had it shipped to the States in the mid-1960's. Why the original screws that attached the top were replaced is a mystery. 
I'll post an image of the guide for large file drawer. I'd appreciate any help in finding a replacement.

I'll post some new images of the desk. The top had a slight bow which I've straightened. 

Is the particle board and lighter wood cross framing original, or part of the bow remedial effort?

Everything about the desk is original. Nothing has been replaced or refinished. I took off the desk top, moistened the back surface,  then clamped to 2x4's on edge for several days in my workshop. 

Here's an image of the drawer guide tktoo. The end that slides in a t-slot on the drawer cabinet is completly gone. As you can see the Phillips wood screws have been replaced with the traditional slotted wood screw.

Perhaps this:
http://www.rockler.com/center-track-and-slide-glides
and you might need to change out the piece it slides on. Or perhaps you can get very lucky and find exactly the right profile plastic slide guide. For what it's worth, I don't think anyone is going to penalize you for replacing this pair of parts with nearly equivalent functioning ones. You can always keep the old broken parts to pass along with the desk if you want. 
As to the designer, I did a bit of looking. I don't ever remember seeing H.P. Hansen pieces credibly credited to anyone.  But it is possible to find other similar HP Hansen desks --attributed-- to Svend Aage Madsen.  Stylistically it would be a better fit.  And his authorship could easily have gone unnoticed, especially compared to Vodder.  

Thank you so much for this information, Leif.. Hopefully there's something that will work. My alternative is to 3D model The part and have a 3D print of the piece made. I have the resources to do that.
As for the designer, I've just gone by research on the Internet, When viewing mages of Arne Vodder's designs, an image of this desk and many other of his KNOWN desk designs, are grouped together. One characteristic that stands out is the desk leg design. Many of his desk, sideboard and chair designs have this signature look. 
There's a dealer in Palm Springs that specializes in mid-century Danish Modern furniture, and they feature several designers work, especially Hans Wegner and Arne Vodder pieces. That's only a couple hours drive for me. My son is sending them pictures and hopefully they can verify the piece. I'll mention Svend Masen too. Thank you.

I really don't think this is a Vodder design, I have nothing to back this statement up so I am more than willing to eat some humble pie if any hard archival evidence can be forthcoming.
Gut feeling is this is another Vodder attribution germinated by someone online that is conveniently cited by others.

Another similar Vodder signature style are the "winglets" on the outside edge of the desk top. This is seen in many of his desk designs and side board designs. Needless to say, it could have been copied by a designer at H. P. Hansen's.
I can't disagree with your statement Howard, that one person may have stated this desk to be a Vodder design desk, and it's just carried on. Unfortunately, the seller at Refine Modern has not disclosed how he came to claim the desk being a Arne Vodder design desk. I've received a reply from the shop co-owner near Palm Springs that specializes in Arne Vodder, Hans Wegner and other mid-century Danish Designers', and she thought it may be an Arne Vodder design desk, it has the look. However, the expert appraiser is in Denmark purchasing furniture for their shop and I will need to wait for his return to get a definitive answer. Perhaps he has an appraisers catalog and can simply look it up.