Why not just sing to ** self 
Failing that genius idea hehe why not do what someone said and get a solor powered radio as i dont think theres solor p mp3 players yet.
If u get a mp3 player anyhow with £50 quid worth of batteries hehe make sure its got plenty of space a few gig maybe so you can put a good mix of stuff on as theres nothing worse than hearing the same music over and over again if ** on a long journey.

Failing that genius idea hehe why not do what someone said and get a solor powered radio as i dont think theres solor p mp3 players yet.
If u get a mp3 player anyhow with £50 quid worth of batteries hehe make sure its got plenty of space a few gig maybe so you can put a good mix of stuff on as theres nothing worse than hearing the same music over and over again if ** on a long journey.