The one I used was
White Rabbit Express, but it was over a year ago, so hopefully it is still operating. I used them to buy a toy from TTM that was listed there for AU$55, and when I bought two of them, all of the other costs (postage & fees) added about AU$30 to each toy... a lot, but then, postage from ebay sellers can be just as bad and I didn't have to pay a mark-up on the actual toy, which would have been at least AU$100 on ebay anyway, making this a cheaper option for me at the time.
Most Transformers items that are TTM exclusives in Japan get released through Hasbro Asia as well, so look for online stores in HK, SG and TW, or ebay from those locations when it is released.