I swear I saw a keychain TV (VHF) on something like Banggood once, for a couple dozen bucks. Really wish I'd bought it for the novelty value, as I can't find it at all now. It would have been a remarkable example of technology reaching a peak immediately before it goes obsolete.
edit: Holy shit, I found it! It's a Mytech MT-010. Can be had for 20 bucks, if it ships to you at all.
Cool, I'll check it out. I still have a Sony watchman. But it can't decode the new signals of course.