@recordbore, I used to live in Japan a number of years ago. If it were me, I would be more focused on hitting the tons and tons of vinyl shops there. So much more high quality vinyl was pressed there than in the US or EU.
Before you go you may want to familiarize yourself with who (what company) pressed what vinyl. The King Records Laboratory series are all demo type discs, The DOR/DAM releases pressed by Toshiba-EMI at 45 RPM are all demo discs. Some of the jazz titles pressed by Nippon Phonogram at 45 RPM are really excellent.

