I use the Nikon rubber eyepiece, the Nikon DG-2 2X Eyepiece Magnifier, and the Nikon DR-3 Right-Angle Eyepiece Viewer on my Nikon SLR cameras and on my Fuji medium rangefinder cameras.
Great video. I love this camera. What type of rubber eyepiece (viewfinder) is that? I would like to buy one for my GW690, but I can't find one that fit.
IIRC the eyepiece thread is compatible with Nikon F (found googling that FM/FE/FA). Nice video! I agree, and made the decision in 2014 before increases of everything that this was a good camera bang/buck. IMO on paper the Mamiya 7 and GF670 better it for travel, but it's a lot of 6x9 frames with the cost difference!