I just bought one from these guys on Ebay. The whole shaft. It's not a square shaft but it did match up to what I had (sort of a triangle). Under $100 to ship to me. Just what you get at TSC for a lot less.
I got it because when I bought my tractor it came with a RC and FM, but only one (1) of the shafts that attach to the tractor. I got tired of moving it back and forth.
LOOK! PTO Shaft for 5' Bushog, BRAND NEW - eBay (item 260239605660 end time May-18-08 20:24:11 PDT)
LOOK! PTO Shaft for 6' Bushog, BRAND NEW - eBay (item 260239605848 end time May-18-08 20:25:12 PDT)