You may not need a transformer, the battery charger I got from the US caters for 110V and 220V, so check this out, the rating is on the charger. then just snip the plug and stick a 3 pin on it. The charger may also be used as mains power to the camera depending on the camera type and what was purchased.
From experience — if you do need to buy a Eur~US transformer, ring a good general hardware shop for a quote. They're often cheaper than hi-fi/photo/electronics outlets...
I would be very surprised if it is not a universal charger,
just check like last post said and look for 110V - 220v.
All you need is to then buy an adapter plug usually about 5 euro ,I think my cost or as was said snip wire and throw on a 3pin plug.