My reccomendation is to send it to a gunmaker who TIG's. Your corner welding shop probably has people with the welding ability to do it, but not likely to have proepr gun knowledge. When I was younger I worked in a fab shop and people would walk in off the street with a broken gun a couple of times a month. I was the only gun crank working there, so I was always involved in the repair/modification. Looking back now, I shudder when I think about what we did to those poor guns. I ownder if some are still useable today.
About 5 years ago, Steve Hughes had a 2 part article in Shooting Sportsman about TIGing guns. He tried to drive home the point that welding ability was only half of the equation, with gun knowledge being an equal half.
I make guns, and TIG, at least 5 days every week. I often hear people say "it's easy, all you have to do is XXX." This is a sincere statement, but they are almost always just echoing what they read on the internet or in a magazine. While they have the best of intentions and may know the Cliffe Notes version of what needs to be done, the devil is in the details and this is what they have no experience with.
Would you let a tool and die maker at your local machine shop make a new pendulum for your Rolex, or would you send it in to an authorized service center?
