In the 1987 Sony introduced a solar Walkman, you can get solar panels to recharge the new Walkmans (also known as iPods) – but this might be one of the few with a solar cell built in… – “The famous “Solar Walkman” was indeed a technological marvel. Not only was this model solar powered, it was also exceptionally compact and fully featured, including auto reverse, metal tape compatibility, Dolby B NR, AM/FM stereo radio and a waterproof “sports” case. Text copyright Â© Walkman Central. Unauthorised reproduction prohibited.
Sony had made a solar battery charger for their “AA” sized nickel cadmium batteries some years before, but the WM-F107 took the concept a stage further. The amount of power required to run a quality cassette player is not… The WM-F107 was quite expensive and only sold in limited numbers. Having produced it, Sony did not see fit to repeat the exercise, and there has not been a solar powered Walkman since…” – Link.
You can find them on eBay once and awhile, usually for $100, but they’re really rare. Walkman central (not affiliated with SONY) has tons and tons of other old school Walkmans too, great site.