Don't waste your time, there is little for sale in Japan which can't be found in other countries. Not only that, but the prices for such parts are actually less in America than they are in Japan. In Japan you usually pay 20% to 30% more than what you would pay in America for the same part.
On the other hand, complete cars are cheap here, I can get a 90's RX-7 or Skyline for a fraction of what one would sell for in Europe or North America.