Is anyone familiar with an aftermarket Rear Rotor for the Harley Trikes. HD Rotors are $256.00 each. Doing research I find very similar rotors that fit older Mustangs and Mazdas. The rotor is a typical 4 lug Top Hat rotor. I find it hard to believe that Harley designed that rotor from scratch. I believe that they are for some previous Auto or something, just trying to find out what. Any help will be greatly appreciated. Thanks Mike