I'm not aware of any PocketPC or Palm GPS company that offers support for Japan. This includes Garmin, who is generally considered the leader in GPS systems. There is no listing of maps of Japan on their web site.

I did find this web site:
http://www011.upp.so-net.ne.jp/mametaro/index-e.html

It appears this person offers a freeware Janpan map for Garmin GPS.

Magellan, the other GPS leader does offers a Worldwide Base Map for its systems:
http://www.magellangps.com/en/produc...asp?PRODID=182

I can't tell from the description if it meets your needs.

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