Where can I buy a Stax amp power converter?

Need to find a new/used power converter for (Japan import) Stax 323s to 117v (North America). Thx for your help. 
Imhififan-Thx very much. The 500 watt looks like it should work fine from reviews. Appreciate your help. 
Just looked at some pics online. I suspect this model is "internally convertible."

Meaning, with some know-how the transformer can be switched. This is quite common for manufacturers. They buy 1 model of transformer, which they then set up one way or the other depending on the orders.

That may be a much cheaper option.

Thx E. You may be right. I know for sure some Stax are internally switchable as you indicate, but the seller advised me not on this model; tho whether he’s correct or not I have no idea. Like you say- it may just take some knowledge to make the change.