I don't think the scott's are plastic, but urethane. I had some 'on order' for a month from them..gave up.
If you are replacing them cuz you are tired of them getting 'tweaked' all the time, get a one piece top clamp. That distributes shock forces better. I haven't had to reset my (stock) rubber bumbers since I put mine on.
Fredette sells one. Seavey machine used to (JCV220R on DRN)...but I read he wasn't doing it now? You might check with him. I got mine from Seavey. Fit great! No extra/special washers, bolts, etc. Bolted right on with OEM hardware.