if you dont care about a parking brake, snag a right front yfz caliper off ebay and put it on the back like drag boys do with a RF banshee caliper?
and for anyone who has spend any time riding at high speeds in the twisties, rear brake fade is an issue and i have a fancy rotor and EBC pads. i use my fronts mainly to keep the bike from rotating too far while sliding a corner and the rears to slow and then sometimes to get the bike to slide.