Quoted from baldtwit:if someone wants to measure the originals, the closest I found to the right "domed" head shape was u-drive screws....like these:
http://rivetsonline.com/drive-screw/18-8-stainless-steel-drive-screws.html
the shaft may be too fat, tho. I've definitely pulled a few of these out of various machines.
I assume nobody cares about the helix...just the right head shape?
Nice find