oh i should mention that the hrz difference between the 2 countries isn't an issue, some people may try to tell you that tube amps will have a weird buzzing sound because of the 50-60hrz difference but this will not be audible if it is at all present... so ignore that potential problem!....
here's some eBay transformers to get you started:
800w - The model I have
Another 800w, lighter weight
300w - cheap and light but might not be enough overhead
You must find the technical specifications of the amp to find the total wattage requirement... you might notice the Peavey poweramp is "50/50" which means stereo 50watts = 100w total..
This is NOT the wattage the amp requires and so a 100w transformer will be DANGEROUS to use with it, my amp is 500w so double check that you know the power requirements of the amp you are buying and that you have a transformer that puts out more than that, using a transformer with less capacity is simply dangerous to the equipment and you!