Forensic , what's your max playtime you get from that 4hour charge? You should be able to get a minimum of 3-4hours of playtime.
i found 2 ads from an ebay seller digistreet in Hong Kong
http://cgi.ebay.com.au/Battery-Cell-...QQcmdZViewItem
http://cgi.ebay.com.au/Battery-Cell-...QQcmdZViewItem
Both has it's dimensions listed, so i'll suggest that you open your player first and measure the max allowable space.
This seller sells USB cables too, perhaps you can take a look. I would not recommend purchasing an AC adaptor charger, as those units from ebay are kinda dodgy.