"Probably you can find there a company which either has already an existing part, or one that could make it for you. For cameras like the F3, of which about almost 800,000 units were built, or the F4 with about 600,000 units, that could be economically possible."
At some point, someone will do this. Anyone who doubts this should do a search for Nixie tubes. I would think the challenge would be to figure out the specs of what to make so it can be integrated into the Nikon cameras without issues. Probably not an issue if you dabble in that. A run of 20-30K would be probably be a good target.
Cameras are quite durable precision devices, and if you think of relatively simple construction of a Leica M, I think many models of our favorite camera should be operational and repairable for decades to come. Unless #disaster etc. Recall that all manufacturers especially Japanese had many sub contractors that did specialized manufacture and those still exist. So you could surmise that with enough cash and connections, yeah, Seiko or others might make you a brand new Copal shutter.