FlightPhoenix
Not sure if JAL hires for their mainline outfit, but JALways hires thorugh WASINC and Hawaiian Aviation; check the websites.
I have heard the odd JAL callsign out of Narita made by a westerner, but more often it is JALways. At any rate, perhaps EKBirdcage or LostInAsia can shed some light for you, or just check out the contract agencies that I have mentioned.
Good luck.