Mid-Century Lamp  

You could also do a short, wide drum,
maybe..?
But if you wanted to do a tall drum, you can always put an extension rod thing between the lamp base and the socket part, though it would entail unwiring and rewiring. But then you wouldn't have to hunt for a tall harp.

Oh, hey-
lampsusa.com has harps up to 15".
http://www.lampsusa.com/search.aspx?category=3013

The more I look
atlook at it, the more I wonder if it isn't perhaps the wrong color for the room. The room will be featuring warmer shades; moss green, orange, yellow, brown, and I'm not sure the blue tones of this lamp would go at all.
If it does stay, it'll definitely get a tall drum shade. Thanks for the link, Spanky.
Eric

lamp harps..
Another place for long harps (or shorts ones) is Antique Lamp Supply and if perhaps you are in the Portland Oregon area Naomi's Lamps Shades is simply the best on the west coast. No web shopping sadly...