It takes months to play that much for me. If you can't use the usual, snap up any old Android phone and it usually has a brightness control. Most take 32GB memory cards. To get a week of playtime I added an USB battery pack.
I'm trying to find an Mp3 player with a lot of space and really low brightness. I'd considered the iPod shuffle but you can't select which songs you want to play. So really anything with a screen that is not very bright would be great, I remember there being Mp3 players with screens like a digital watch but I can't remember what they're called and they probably have really low space. If anyone has any suggestions that would be great. Thanks