Connecting Bolts Tecno Nomos Table  

Great find Rensebrink, have you tried testing one of the screws if it fits, maybe you just need to find more same screws or bolts from a hardware store?
Have you checked with the manufacturer where to get replacement bolts/ screws or if you could purchase from them directly or a showroom in your area that sells furniture by Tecno? The site is called tecnospa.com
Although Sir Norman Foster originally designed this as an office furniture, most ended up in a domestic setting as a dining table, the glass top versions displays the base well.

Thanks for the reply!
Yes I went to the hardware store and bought several bolts, but they where all to big or to small. I also directly contacted tecno's headquarters, but they never replied unfortunately. But I haven't tried any local distributors yet. So I will try that next!

You probably tried it already but I meant to say is to try one of the hex bolts/ screws that is in use in your table base now to see if it will fit the empty hole with the missing bolts, then at least you can gauge if it needs the same size as what you already have (or maybe shorter or longer?) to properly secure your table top to the base. If you are somewhere in Europe it should not be a problem finding metric size bolts but if you are in the USA not all hardware stores will stock that except the specialized ones. Also if you think you need the same size bolts, always bring one to the store to compare, just make sure that your table will be safe and secure temporarily if you ever remove one. Good luck.

FWIW, the fasteners in place on your desk are called "socket head cap screws" here in the US and are available in a wide variety of alloys, sizes, and thread pitches. The empty holes in your photo appear to be recessed for these, though it is unclear as to what the missing screws would thread into. Are pieces missing there, too?
As mini suggested, try one of the existing screws to see if it might fit and start from there. Industrial fastener suppliers and/or a local machinist would be the next step.
http://www.mcmaster.com/#socket-head-cap-screws/=14ct2kj
https://www.youtube.com/watch?v=66HUDL40EHk

I may be completely seeing this wrong, but it looks like the missing bolts, which are "socket head cap screws" as Tktoo noted, go into a channel. You will need the appropriate nut to place in the channel. I would assume that the nut is square, and only slightly smaller than the channel width. But again, maybe I am seeing this all wrong...

All the remaining screws in the table are bigger than the ones I need. But the other screws indeed look like socket head cap screws. There are also markings on them. For example: 1 5 F 1 8.8 or O 8 V 8.8
I'm not sure if that is correct, since it is very hard to read. They can be loosen with a 6mm hexagonal wrench.I got some M6 and M5 socket head cap screws, but they were either too wide or too small. This weekend I will try a specialized store in non standard screws, maybe they have a size in between M5 and M6.
For the record, no other pieces are missing, The frame should directly connected to the steel structural beams which are attached to the tabletop.