I have two black 1950s versions with the metal dial. One belonged to my grandmother, probably since it was new. The other one, I picked up at a thrift store.
I just noticed that the one from the thrift store has some sort of adapter on the end of the wall cord, that allows it to plug into a modular jack.
So, J, (Kirbyman65), they might not be easy to find any more, but that's one thing you could look for. I would imagine you just match up the colors of the wires, and viola. You have a modular plug!