Thanks for the ideas.

I am in touch with my local plumber here in NJ (a good guy) and he suggested possibly using what he called "plumbing epoxy", which he says hardens very well and is waterproof, can be sanded, and possibly multiple layers applied to fill in the existing hole.

So this is simlar to your suggestion, but not requiring a metals shop. The old pipe is brass with now very worn chrome plating (mostly gone). My concern is the back side where it had worn away is now quite thin (80 years of flushes!).

This small hole is on the back side near the top where the pipe meets the flush valve near the entrance to the tank. It is probably just below where the nut with the gasket will sit once it is all put into place.

So if no replacement can be found (and I just called DEA in Murphy's, CA -- they have a 3" offset at most), we may have to go the "repair the pipe" route.