I was about to suggest that Radio Shack might still have a battery powered radio, but you've pretty much found similar sources.
If you want authentic and cheap, you still can find one of those alarm clocks that you wind up every night for <$10 at Walmart or Walgreen, Target, Kmart, and the like, or could the last time I looked about a year ago, when we couldn't find the one that was supposed to be stashed in the camper.
(The camper has a built in clock radio CD player with an alarm clock, and runs off the battery; but since we don't much like thinking about such stuff when we're camping we've never figured out how to set the #@$! thing.)