I see you haven't gotten any hits on here, I'll throw my advice at you if you don't mind lol.
Used clutches are a big mystery and gamble, even if you can locate one that's in tight shape or rebuilt, you should definitely have it balanced. All this is even more important with a big 900, clutch health and balance are CRITICAL with these engines. Look for a clutch with the electric start ring gear on it... the extra weight is said to be a great help for the 900 which has too little crankshaft mass. The extra bonus is that when buying new, the ring geared clutch is alot less expensive for some reason.