The problem is that Buffalo is not allowed (due to a patent lawsuit) to sell any flash-memory related products in the US. As far as I know, these are only available in Japan. I vacationed there last month and picked up three, which went to various members here - I have no more. User bollywood also got some and resold them.
I am not aware of a Japanese retailer that is willing to ship these to the US, but one never knows. I'll point out that, in addition to the packages combining the adapter with a SDMicro card, they also offer packages with the adapter alone, which is what I bought. Given that the memory cards alone are cheaper in the US than in Japan, that would be the preferable way to go if you can find them.