From some info I have:
wmberg.com
These are aluminum replacements:
The two small gears, forget which one goes where.
part #p24a66-14
part #f24d5-28
The big one's are trickier. Everyone say you just need to ask them for this part# and to drill a 3/4" bore. Only problem I believe is that is the diameter of the hub, so you need bigger hub too.
part #P24A68-60
I think this is a delrin plastic version of one of the 28-tooth one.
part #P24D28X-28
Let us know how it goes. I know some people have gotten them, but feedback is always good.
Edit: Anyone got an extra springs, hardware stores around here suck?