4 REAR WISHBONE BUSH SET FOR BMW E53 X5 | eBay

BMW E53 X5 Passenger N/S Rear Swing Arm Wishbone | eBay

Are either of the above any good?

You can also try partsgateway.co.uk. Came up trumps for me for every time.

Also, are you 100% sure the bush is bad? I had a look at mine the other week while I was in the vicinity for something else, and thought they were shot. But upon closer inspection (using a lever to try and move things) I realised it was the outside portion of the rubber that had deteriorated and not the bush itself.