I went to Yodobashi in Kichijoji last weekend and the K-7 had sold out...
You could try Fujiya Camera in Nakano. They've got a huge selection of new and used kit.
Exit Nakano station North exit, and see KFC on your right. It's in the narrow back streets behind there( actually 3 camera shops).
Akihabara would also be a good bet. It's not called "Electric Town" for nothing.
Failing that, check this link:
????????????????????:???
Good signs from that link frank posted.
It's an online price-matching site. With 7410 comments about the camera and an overall 4.82 rating.
Also, currently #6 ranking from #12 in a week.