They're not bushings, but needle roller bearings.
I bought some from CBC bearings -it ads up though ($): it cost me about $50 for 4 (and there are a total of 6). You need to retain the pivot shafts as the bearings are sold with the race and outer only.
Before you go rushing out to buy a new set of bearings I would investigate your shock bushings, these are the more likely source of play (bearings have to be REALLY farked before they develop play. ie the bike would be making horrible scrunching, squeaking noises if they were that far gone.