I had just buy a beautiful zorki 1 camera and I very happy with it but as I wear glasses I cant use the composing finder properly. I was thinking about making an auxiliary finder (50mm) myself. I know it's easy make one for short lenses (25-35mm) with spare parts of a disposable camera but I wonder if there is a way to make one for 50mm.
Instead of DIY I´d look out for a Voigtlaender "Kontursucher" - they are not that rare nor that expensive and they apply a stunningly simple, yet clever principle.
Instead of explaining it, look for yourself ;-) - it´s in german, but you should understand the principle by looking at the images:
You mount the finder on the camera and hold it front of your face - keep both eyes open. The left eye will see the situation, the right one will "catch" the viewfinder frame while the brain makes a composite image of the both.
I often find it helpful to use an open-frame finder; no optical parts to intrude in terms of magnifications (positive or negative), no chance for fingermark, perfect brightness etc. After all it is an aiming device, which frames a slice of reality before you within the four edges of a rectangle.
Leica, among others, produced frame finders, their designs can be used as references for constructing your own; one for a single focal length would be a simple job I am sure.
I am unfamilar with the details of the Zorki. Perhas if you visit a local optician they can make you a correction lens to install in or on your camera.