eBay My World - massive_speed_system
There's the ebay page. they didn't really keep me up to date without asking first, but other than that can't beat the price especially for clutch masters.
edit: not only do i need a clutch to hold lots of power but i always figure i go overkill on the clutch so i know it will hold. with all the good things morgans432 says i don't see why you couldn't use one that'll hold alot. it shouldn't be like the ACT where it's a leg press if you use the extreme pp.