I don't think there's a very strong aftermarket for them yet. I'm not even sure Ford offers all that many parts for them individually. In the end it would probably be cheaper to just pick up a good used one from a yard.
There is a mt82 website that sells them, but Ben Calimer is prob going to be your best bet. He has rebuilt a few that use the rebuilt kit you find online and posted pics of some of the bronze shift forks that replaced the OEM plastic ones and they were scarred after 1000 miles. I believe he used his own parts that he doesnt sell