http://www.blacksmithbolt.com/index.html
I just saw this website noted on another forum with regard to locating old style hardware and fasteners. A search through his site shows all kinds of fasteners, rivets, etc in the old style that we crave. He has no phillips or robertson head, and no zinc plating on the bolts Apparently he will also help find screws that are not listed in the old patterns. Unfortunately he does not list hex head bolts.....too modern for him.
http://www.blacksmithbolt.com/gpage34.html
On the above link, for instance, he has the drive rivets like you would use to secure a data plate onto a bren carrier, or the safety pin retaining chain on a pintle hitch.