Sorry, I don't know any.
I am going to do a web search to find out.
Did you try the J-pop section on itune and last.fm?
Ok, from itune Japan:http://itunes.apple.com/jp/genre/id27
Thanks pyree, unfortunately I can't read japanese and I'm a linux user. Why can't we just buy all the music in the world on one simple site
*update* as far as the song i'm looking for goes I found it on the site but I need to research how I buy the song from the japanese itunes with dollars not yen.