email Core Moto. Tell why you think you need a new rear brake carrier. If the problem is just that you have a rear brake carrier for a CBR, you can use a rotor with a CBR bolt pattern provided it's the proper diameter to fit to a Hayabusa caliper.
My front Carrazzeria has a bolt pattern that ONLY fits a bolt pattern for a CBR. There are no carriers on the front, there's just boltholes. I still used that wheel and rotors on my Kawasaki as I would a Hayabusa or any other bike that had the same diameter of OEM rotors.
If you must use a rotor with a Hayabusa bolt pattern, I'm sure Core Moto can set you up with the proper carrier.
If bolt pattern is not the problem, if your carrier is broken or has stripped boltholes, etc, Core Moto will be able to provide you with a replacement.