Need new MP3 player battery
 

I'm not sure where to post this, but my MP3 player's battery is running out in a very short time period and dropping fast. I recall, upon first getting it, that it lasted 18 1/4 hours but now, it's hovering around 11 1/2 hours and this is dropping fast (at an accelerating rate too). Do you know how I could get a new battery for my Creative MuVo2 player (4 GB model)? At least, what battery do I need to get? Thanks.