There aren't any U. S. dealers for one simple reason -- the Russkis long ago stopped making the cameras. That's why the famous line - the first two digits of the serial number give the year the beast was made.
I have three FEDs, nine Zorkis, and three Kievs. Most were bought on evil-Bay and two or three from Fedka in NYC. Yuri at Fedka is a highly dependable dealer. His prices may be a little more, but you get what you pay for. He goes over his stuff and makes sure it works.
Keep in mind that, as you can see in these forums, quality of "FSU" cameras depends largely on how much vodka the boys consumed the night before the camera was made. Which is to say, it's variable. However, the lenses have a good reputation, so if the camera body functions as advertised, you're home free and will get good pictures (if your EYE is suited to such).
A number of threads have been posted regarding different dealers in Ukraine, Russia, etc. If you see something interesting, ask about the dealer. You are pretty sure of getting a response.