I believe they just used car radios. If you could
find a picture of one with a radio and search
the pictures of car radios from that time you
should discover what brand and year they used.
Once you find out the brand finding one shouldn’t
be difficult. If you find a picture of one in a boat
post it. Some of us here may recognize it from
owning the cars from that time.
Tubs
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.