Japanese aircraft? Not too many of those around in this country, except for the few we got to see in dubya-dubya two. For the most part Japan buys NATO airplanes for defense and both US and Euro airplanes for commercial. I do recall that Honda is investigating a joint venture with GE to produce a aircraft turbine, and another venture with Teledyne/Continental to enter the piston engine market, and Toyota built and got approved the Lexus-based V8 engine for light aircraft use. Rumor is also strong that Honda is going to pursue a small 4- to 6-passenger personal jet, but nothing is firmed up.
There are a few light airplanes from Germany, such as Aerospatiale and/or Socata, but they have merged with EADS to become EADS/Socata. Other than these few, for the most part Europe also flies US-built light airplanes. In the defense and commerical arena, you're no doubt aware of consortium aircraft such as EADS (Airbus for commercial, Eurocopter for rotary, Eurofighter and A400M for defense), and Fokker and ATR (French/EADS) come to mind in bizjets and light regional jets. Given these are European consortium, they are likely all using standard metric hardware.
I don't know for a fact, but any country's aircraft industry is likely using the same standards as in their cars. Common country, common fasteners. Germans use "standard" metric in their cars, Japanese use JIS (finer threads).
I suppose you could always call your local big airport and find someone that is equipped to service and repair Airbus. They'd certainly know what fasteners are used and may considering selling you a limited amount. But you better plan on spreading your cheeks...
