I don't think your alone. Not to long ago I had a guy give me a receiver and a bag of parts for a old Chicago Arms Single Shot SG. (I was at a outdoor trade show and was not prepared for this nor did I have my own booth) he tells me he found it in his grandfathers basement. He wanted it back together, he didn't know what was missing besides the fore end and barrel and he didn't care what it cost to have the parts made
Being a student of the gun smithing trade and wanting any experience I could get I gladly took it and completed it for him but there was absolutly no info on this gun anywere, parts were just non existent.
I have found that most of my short gun smithing career is making missing parts. Many time all I have is a picture or sketch of the part. No dementions and rarely the actual broken part. Some parts are just unachievable w/o casting the part. many can be made from scratch but done through a trial and error process. Unfortunately for most its just not worth the cost.
If your in luck you might find yourself not alone in finding these parts. A machinest or gunsmith might be happy to pick up the work to make them. I found a guy looking for a firing pin for a CZ38. I told him I would be happy to make him one if he had the parts to the broken original. This job turned from 1 pin to 8 from different owners. It benefitted them greatly b/c the cost to make them when down from just making 1.
Times have changed, those old closet queens are making a come back and sadly most of them will never fire again.