I have the following:
54m/c Sinarback adapter for fuji gx680 series
$299 obo
54h/s sinarback adapter for gx680 series
$239 obo
Sinar control cable for sinarback to gx680
$69 ea or $29 with an adapter plate.
Kapture group stitching adapter for gx680
$390
I also have a set of standard bellows and a new in package waist level II finder for the gx680.