Dear Bipolar Mom,
One of the primary difficulties of this illness is stabilizing it. Since I have so idea how "sick or well" your son is, it's difficult to know whether he's capable of working now or not. Perhaps the real goal needs to be finding a way for your son to to engage in activities that will make him feel better so that he will have a more positive attitude about recovery.
If he taught in Japan, then perhaps he's open to meditation. There is continuing evidence to support that meditation may have a huge impact on this illness as well as yoga. The two best sources I know about are the work that has been done by Jon Kabat-Zin on Mindfulness Meditation and Amy Weintraub's book on Yoga for Depression.
If he could begin participating in these activities, then perhaps his life view would change. I'm sure your son has a lot of terrific skills that he could use in jobs unrelated to teaching--if that's not what he wants to do any more. Also, since he must be fluent in Japanese, I'm sure there are freelance translation jobs as a way to work at home--in the short-term.
However, the key is feeling like you're capable of working. And the information on work seems to be geared to people who are interested in working in the mental health field rather than on people who are bright and capable and just can't figure out how to restructure their work lives. Still, I did a little research and the following is the best I could come up with.
I recently found a site, the National Empowerment Center, that I felt was uplifting. It was founded by Dr. Dan Fisher, a psychiatrist who has recovered from schizophrenia. Many of the recovery stories and the people involved in this organization seem to be living and working with bipolar disorder. It certainly would be worth an email or call to find out what they know about work-related assistance.
I also read about a program at Scripps Hospital in La Jolla, California. They have A-Vision Volunteer Service Program with the goal of helping people who suffer from a serious mental illness re-enter the workforce. It's a partnership between The Mental Health Association, the Vision Program, and Scripps Mercy Behavioral Health Center. Maybe they know of similar programs in your state.
The Depression and Bipolar Support Alliance has a page where they list resources--although I have no idea whether these are truly viable and helpful organizations or not.
The Center for Psychiatric Rehabilitation may have information. I just did a google search on them and don't know how helpful they will be.
I wish I could give you better advice. It's either unavailable or I just can't find it.