Get local businesses to contribute to a local boy with a mission.
It's a matter of having a good proposal that you can put in front of the owner that shows an enterprising young man with a vision. A lot of local business people are often willing to make a contribution - try such folks as car dealers, banks, and such. That's where the money is.
Other ideas for creative fund raising is having your son offer to work for his cause, odd jobs, cleaning up lawns, etc and let them know his purpose. Covert hours to dollars! Likewise, friends and family members are also often willing to make a gift. Honor a relative via birthdays, anniversaries and special occasions by contributing in their name to the send a boy to Japan as an ambassador of good will, global understanding and world peace. Something like that. And good luck.
Email me your address and I will send a gift.
Finally, make sure that your son follows up each gift with a note of thanks and a promise to report on his trip. Get some local press coverage, yes, good ideas all.