I've got all of them still working, but don't really want to part with them. However, over here on ebay they are dirt cheap:
http://video-games.shop.ebay.co.uk/..._catref=1&_fln=1&_sop=1&_trksid=p3286.c0.m282
and for small, cheap items like that, shipping isn't expensive at all
have a bump
=EDIT=
Reading the other posts, you can indeed change the batters, you just need some small pliers, a new battery and some tape, so whether or not the battery still has life and you can save or not doesn't matter, you can sort that yourself