If you want one, just break the B+ somewhere. A real easy spot is the two red wires from the transformer. Insert a switch there and it turns the B+ off and on. DOn't even have to pull the boards.
But really, why bother? Back when everything was tubes, table radios and TVs didn't have standby switches. Nor did the Hifi in the rec room. On somethng that small, I don't think cathode stripping is an actual issue.