There are loads around - Maplin is one place to start.
I bought this one and was prepared to put up with the smaller screen so as to have SD and USB capability. It has its own battery and charger but does seem to take ordinary batteries as well. It also plays DVDs with mp3 music on them as well as the usual CDs with mp3s. The screen is, however, bigger than most cameras and phones. The sound is excellent through a good set of 'phones but it also has a built-in (tinny) speaker (has output to TV and to surround sound).
http://www.maplin.co.uk/Module.aspx?ModuleNo=2 22912&doy=9m7&C=SO&U=strat15
I paid �69.99 but it is now �59.99.
Looking at the Maplin site, I now see a dearer one (�99.99) that has the more 'normal' 7 inch screen with SD and USB (bummer).
http://www.maplin.co.uk/Module.aspx?ModuleNo=2 23359&doy=9m7&C=SO&U=strat15
but not sure if it can take ordinary batteries.
Have a look at Currys (and Philips models) or Google away.
Happy hunting - let us know what you settle on.