I've seen them while looking for wheels multiple times. Kept it in the back of my head just in case I decide to go that route, but searching "gsxr 600 bearing" and it comes up with a few irrelevant listings as always, but there are auctions for what you may be looking for. I just try to be a little vague with ebay searches because sometimes people list things with screwy or alternative names. Often times though they seem to load up their auctions with key words you might search for just to get eyes on their auction. Probably a good idea to double check anything before you buy it.