100 volt change to 120 volt power supply? Diezel VH4, Herber

I have an opportunity to get a killer deal on a couple of Diezel amps (VH4 and Herbert) in Japan. Alas their power supplies are set to 100 v.

1. Can I use these amps in the US without modification?
2. If I can't, is it possible to modify them to the US spec and what's involved?
3. If the power supply is swappable how much is a 120 v power supply and how can I get it?

Thanks much for your help.

peterdiezel (at) diezelamplification ( dot) com