Here are two universal cell phone chargers:
Charger for pins accessible on the edge.
Charger for pins accessible on flat side.
More searching and you can probably find both types on eBay.
They differ only in access to the battery's poles--just take a look and see which would be able to have its pins contact your battery.
I've used both types successfully on cell phone and MP3 player batteries. I forget which one I had that put out only ~250 mA, but it worked for cell phone batteries.
You have to find the + and - poles of your battery (if the poles aren't marked), but both types usually have some indicator system that helps identify polarity.
I also don't trust their safety, so I am usually nearby for the first few hours, and then check that the heat generated in the battery is low.