I see you have the Sony PRS-T1, so do I. But I have the Japanese firmware, this lets me connect to Sony's Japanese Bookstore over WiFi. I had no problem registering there with a non-Japanese e-mail address nor problem with using non-Japanese CC.
So you might try loading the Japanese firmware. Should that not be possible it is absolutely no problem registering for a Japanese e-mail address with Yahoo Japan, and then you can buy from Kinokuniya.
PS Ohh, I see this is your first posting. Welcome to Mobileread.