Paul - without looking up the schematic, my guess is that this radio uses an electrodynamic speaker, which means that you cannot get a speaker to replace it from a modern supplier like radio shack, although with some circuit modification, you could make a radio shack speaker work. I think Rene has given you the best advice - rund an ad in ARC. You do have to be a member, tho. Their website is www.antiqueradio.com.
good luck - Jim