Keep up with KEH... SQ 135 W backs appear from time to time... I waited and got one.... and one for the ETRS(i), too ...... tricky little buggers to load but they really work.... took one to Maine.... wow... used Fuji 1600 all the way!
Good luck
Logan
Quick question ... I notice that even on the 135N that the cutout in the back (when darkslide is removed) the aspect is panoramic .... so does this mean that the inserts are interchangeable, or are the actual entire backs different?