You might want to go at it this way:
It should be fairly straight forward to get the major dimensions--height and length--by simply measuring.
The tricky part will be sorting all the other cuts.
For those, I would start with a heavy kind of paper, cut out a rectangle that will cover the body, anchor that to the body (maybe rubber cement in a couple of places? Something that will keep the paper in place but not permanently), and then trace the other cuts you'll need to make: the lens flange, self timer or strap lugs, screw heads, etc. Once the paper fits well, you can then use that as your pattern for whatever leather you're wanting to have as the final cover.
Another way to do this might be to use masking tape? (Preferably the type actually intended for masking paint as it is not as sticky.) I'd try to find some in a width that is wider than the camera body is tall so that you are using one piece. Tape around the body, then cut out the areas that need it. Carefully remove the tape so it doesn't deform, put it on the outside of your leather, cut to match.
I recovered a FED5 by using the paper pattern and it came out OK; if I could have found masking tape wide enough I'd have done it that way.
I know Cameraleahter sells some sheets of adhesive backed materials--and probably some sheets without adhesive--and you can really use anything that you like.
A sharp knife and lots of patience are the big requirements for this, I think.