Ramen place is called Kouchan. It looks a bt run down, gets average reviews (one person marked it down because they felt the bean sprouts were too dark) but I like it.
Another option for second hand bikes is to try the Tokyo Cycle Club website. Their classifieds often have people selling (usually) road bikes before heading back to Euroland, USA, Aus etc. Dont see many fixed gear but could convert a road bike to single speed. You could put up an ad looking for a FG and see what happens. I think it is free.
A lot of the people in that group either bring bikes with them or order from Wiggle or similar in order to obtain the larger frame sizes.
Gambatte.