Someone will correct me if I'm wrong but I'd say, with a cost involved, you might find a machine shop that could weld metal to the existing rotor and machine it to the correct thickness so you could reuse the original rotors. I know they do it to crank shafts on heavy equipment. Just a thought...
I thought I'd add to my quote above...I've been researching the add metal to the rotors as is done to a crank shaft idea. CAN'T be done. My source is several hi-tech machine shops that specialize in the welding of critical machine parts. The one that gave me the best answer to my question is a place called Aviation Welding in Bellingham, MA. They specialize in the welding and repair of turbine engine parts for aircraft engines.
A crank shaft has metal added to a jornal by a type of equiptment that actually sprays metal to the specificly controled heated area much like powder coating would be applied as it's spun. To do this to a rotor would be impossible to do because once the metal in a rotor was heated hot enough to accept welding it would be so brittle when it cooled it would break with the shock of a hard jab on the brakes. Not to mention they would always be out of round from the heating. The worst part of the job would be to even try it to see what would happed would cost over $1000.00 per rotor.
That's why they don't rebuild rotors. Need rotors? Buy new one piece rotors. By the way...I lucked out! My rotors machined and though they are on the edge of being under size I can still use them!