Well Steve I'm not quite sure as to what type of street bikes are sold in 
Japan, but I would imagine that they have many that are similar to North 
america. The only problem though as you have pointed out would be frame size. 
Perhaps looking in bikeshops to see if they have an old model still around 
that you could get for cheaper than brand new. Placing adds in the newspaper 
indicating the frame size you need could generate some possibilities. As for 
the long seatpost that you are using. It does not sound very safe. It would 
be better that you get a bike of your size. Last resort would be ordering 
directly from a dealer or have a shop order a frame for you. As long as you 
do not ask for a racing light type of metal it shouldn't cost too much.
Richard G.
--- Maximus/2 3.01
---------------