Your Dad had the now-mostly-lost knowledge, although there are still lots of people “doing” old radios as a hobby today. My husband Logitech is one of them. We have a bunch of old radios that he restores. Last week he found a very rare Musette radio from 1931 or so at an antique store.
He could advise you on where to get a new tube for your metronome. I’m pinging him to this comment.