I have been using these guys for various old style screws and fasteners. Price isn't bad, and best thing is they are not plated. They are also available in oxide black, which has a nice look and readily accepts paint.
http://www.blacksmithbolt.com/
They have 3 basic rules there: no hex, no phillips, and no zinc. They also add:
Of course, since we specialize in old-fashioned fasteners, you can also assume several additional rules, including but not limited to: No Pop-Rivets, No Torx, No Metric, and No Combo.