Ah yes, the Huffy Radiobike. Many folks think a Huffy was just another piece of junk but the Radiobike was the diamond in the rough. I had one complete. The radio was very tiny as you could imagine but to my surprize it was a tube radio. I was surprised by this because you figure tubes do not take well to vibration. The rear rack held a honkin large dry cell battery pack. The radio antenna ran down the down tube. It was a true middleweight with drop center rims.
Your best bet to find a radio would be to go to the Schwinn collectors forum and ask around there. The old balloon guys hang out there they they can probably hook you up. Be prepared to pay, the dials and battery pack are also pretty expensive.
If you continue to have trouble, drop me a line and I will try some of my old haunts.
Ray Homiski
Elizabeth, NJ