You will find a few 55mm, 150mm, and 250mm lenses for sale every year on eBay and sometimes on photo hobby forums. The rest are apparently exceedingly rare. So for practical purposes the Kowa system is really a three or four lens SLR system. Since the Kowa system has the shutter in the lenses, it will probably always be that way, although I wonder if it might not be possible to adapt, say a 500 series Hasselblad or some other shuttered lens to a Kowa body in some way.