I don't know about the bearings; never tried to find Japanese replacements but the crank seals are near impossible to duplicate. They are an odd-ball size that are not available anywhere but one source. At least that was my experience when I searched. Here's a link to Piston Bikes, Motorized Bicycles Gas Bike Engines Gas Powered Bikes Motorized Bicycle Parts
one of our sponsors, that has a good selection of engine parts. I ordered seals from them and was quite satisfied with their service and parts quality. You might give them a try if you have trouble locating the parts you need. Hopefully your supplier will take care of the issue and you'll be set.