Folding Sport Finder for 6x12?

[Fragomeni]

I have a Horseman 612 kit I’m putting together and eventually I’d like to get the super wide 35mm lens for it. With that lens, the camera is at its most compact and I’d like to avoid the bulk of a standard viewfinder with that lens and instead use a pop up/ folding sports finder. I’m pretty sure there is no 612 sports finder in general, let alone one for 35mm. Can anyone offer insight on how to make one, or better, modify an existing one to work for my purposes? I’m aiming for essentially the same type of sports finder solution used on the Horseman Convertible but for 6x12.