You need to look at your charger (or the instruction manual) and see what voltage it accepts. If your lucky, it will say AC 100-250V or something close. This means its a dual voltage charger, and will work in the US with nothing more than a travel plug adaptor.
If it says 220V only, your out of luck as you will have to buy a 2:1 step up transformer, as well as a travel adaptor.
You can pick up a transformer from the likes of Radio Shak, theres one in the Florida Mall just near the Pennys entrance on the left.
Most chargers are multi voltage these days, and you dont usualy even have to switch them, they should be automatic, particularly Japanese manufactured cameras.