I know many folks that go after NJS frames browse the offerings on the yahoo.co.jp auctions (apparently yahoo rather than ebay is the auction site of choice over there), so perhaps you could find something there. You'd probably need some assistance with communication, however, as I assume you don't speak Japanese, and most sellers probably don't speak great English.

Furthermore, I don't know if Bridgestone or Panasonic's offerings in Japan were necessarily the same, or even named the same as they were over here in the US. I'm not sure exactly how much influence Grant Petersen had on their line over here. Similarly, the Panasonic PICS system was (and still is, for that matter) known as POS (wonder why they changed that one!) in Japan, and I wouldn't be surprised if differences ran deeper than that.