I know that you're in the states, but try looking at Marstar Canada, or Lever Arms, or International Shooting Supplies. (search their names and you'll get the sites.)
We're flooded with SKS's up here (so much so that Lever Sells them by the crate to customers). Anyways most stores up where I live carry a full line of parts and accessories for them. I'm sure that they could be shipped to you - depending on what mood the border guys are in! I see the parts everywhere.