Carver CubeAmp transistor replacement

Hi.

My closest friend's birthday is coming up at the end of May, and I was hoping to repair his Carver Cube-Amp. He thermalled the output transistors, as near as I can tell, over a year ago. The transistors have the Motorola logo on them, but I cannot find a replacement. No one I've talked to, including specialty companies and ON Semiconductor, has any record of them. The few repair places I've uncovered want far too much money to repair it, and the Carver-Authorized Repair companies wanted about $15 per transistor! I'm certain I can find replacements for less!

I'm looking for "C2000", "C3000", "C4000", and "C5000". They all have a manuf. date of 1981.

Thanks

Mark Broker