Hmm I don't know of any teachers in Tokyo being from Los Angeles. However, you can go to
http://www.musicdojo.com and take online lessons there. I've taken many myself and find them very rewarding for the $50 per course which lasts for a month.
Every day is a new lesson explanation and assignment and over the course of a month a total of 20 different aspects of the course end up being covered...all for $50!!
Musicdojo could be a quite pleasant alternative for anyone not being able to find a teacher. I'm pretty sure they have a couple if not a few courses on slap bass itself.
Good luck!