don't think there's anyone to contact! specific parts for these ol radios beyond the common tubes, resistors, capacitors, just aren't made, so you're looking for 'good used'
your best bet will be to watch e-bay for a cheap non-working radio you can scrounge parts from, and also put a note in the swap meet forum, parts wanted here
if your actual volume adjustment works but the on/off part of it doesn't, you could put a toggle switch in the power wire from the fuse panel and mount it under the dash so you can just turn it on and off
good luck!!
Bill
