I had to purchase a few Unit 1/Mk1 foils recently, and found some here in SoCal at Seatek Rigging (
http://www.seatek.info/) and Bahia Rigging (
http://www.bahiamarine.com). Of course it could be rather pricey to ship them back east, so hopefully you can find one in your area.
As I recall, the Mk1 came in 2 different versions. The original used roll pins to attach the foils to the connectors. The roll pins were replaced with set screws on the later version, which worked much better. I believe that the holes in the foils are different between the 2, so you'd want to match what you have.