Hi Ross, welcome to the forum. I'd try Otari first, but I guess there's some changes in going on over there that that makes ordering parts a little tough. You can also try Vintage Electronics;
http://www.vintage-electronics.cc/index.html I've always had good luck with them. I doubt if the capstan belt changed from year to year but just be sure to give them as much info as you have when you order it.
