Heh, this old thread is still around.
I was just at the local Walgreens and found that they had not one, not two, but three different ultra-small earphone radios at $5.99 each, powered by button cells. All of them would reasonably fit in an Altoids tin PSK and each probably weighed under 0.5 ounces. So this is what I was looking for at the start of this thread, a "Photon II" class of radio.
There was an FM radio with a scan button similar to the cheap pen radios we've been seeing everywhere, probably with the same chip inside, powered by two LR44's. Then from another manufacturer, there was an AM model and an FM model, both with analog tuning. The FM model used two LR44's and the AM model used one LR44. The AM model looked like it had a tiny ferrite bar antenna. As I remember, both FM models had pieces of wire hanging from the earpiece, to act as antennas.
I didn't buy any of them so I don't have any test reports, and I didn't have a camera with me so I didn't take a photo. I might go back and buy one of the radios sometime though, probably the AM one.