Look around for a SunTour MG series fork. (1" threaded, elastomer suspension with adjustable rebound) I recently put a SunTour MG-81 on my 1984 Kuwahara Sierra Grande. It's an excellent fork.
What parts of your fork are worn out? If the lowers and towers are ok and you just need to replace the elastomer suspension, seals etc, I'm told by several LBS's that it is possible to do.
Good luck.
~Sherry.
All vintage, all the time.
Falcon Black Diamond
Gitane Tour de France
Kuwahara Sierra Grande MTB
Bianchi Super Grizzly MTB