@russ69 availability of transistors is of a lot less deficit than tubes, but you might NOT find the original ones. The replacement transistors must be matched to parameters and sites like Digikey or Newark.com have charts of matching. The average price tag for such repair is in the park of $300 which can also buy you same type of working unit.
@mike4597 This issue should not be too new for any experienced repair tech around your corner so you don’t have to find any specific "audiophile approved" tech.