Check the bearing dimensions, the 600K bandit also uses a 20mm axle so if the bandit bearings and spacer will fit the GS500 carrier you will be good to go (I can measure the scrap carrier later if that helps ?)
EDIT: just had a quick look on CMNSL - the Bandit 600K, the GS500 and the early GSXR which you have all use the same sprocket carrier bearing (25x62x17) so either the GSXR or Bandit spacer would work with the GS carrier and a 20mm axle (might need the length adjusting) or you could bore out the GS spacer to 20mm
