I mentioned this before in another thread -- I purchased a Zojirushi IH pressure-type rice cooker at Costco in Japan and using it in the US without a transformer. I suspect that because it is microprocessor-controlled that it monitors the temperature and makes adjustments as needed so that the higher voltage doesn't result in higher heat. It certainly doesn't feel hotter than normal. I've been meaning to measure the current draw to see if it is automatically compensating, but just haven't gotten around to it. While it works for me, you'll have to decide for yourself if you want to take the risk. I just thought I'd provide my experience as a data point.

For transformers, check out the Book-Off stores in the LA-area. I have a couple of transformers that step down from 120V to 100V and are rated for 1,400 or 1,500 watts. They were purchased as used items at the Costa Mesa Book-Off store. One is a Sanyo, the other a Nissin. I believe both were made in Japan. Cost was $40 and $45. Book-Off stores in the US buy and sell used electronics, fashion, household, and other items, similar to the other xxx-Off stores in Japan. The transformers were probably obtained from Japanese company employees who were working in the US, before transferring back to Japan.

The transformers aren't too big, maybe like a 5" cube, but they are relatively heavy. Sorry for not having exact details, but I'm currently in Thailand and can't check.

I just did an online search, and I believe that the Sanyo transformer is a model TSD-15U, with the following specs:

Input: AC 120V, 50/60Hz
Output: AC 100V
Power: 1500VA