MegaMacs.com has the Rio 600 32MB MP3 player for $30. These were a pretty good player back in the day. They can also be expanded with memory backpacks, which are fairly expensive, but it might be worth it. Some features are that you can get up to 11 hours of playback on one AA battery, and that it is light, and uses a USB connection.

http://www.megamacs.com/v1/index.php?action=view&pid=1372789