Don't know what happened to my text in this post, but:
My rear brake bridge ripped off my 70's Motobecane Mirage today after I changed the brake cable. Awesome braking power until - pop! I am thinking the best option is to have a new bridge welded on. Any suggestions or offers? I ride this thing everyday to work in The Loop. So I am definitely eager to get this fixed.
When my seat post on my trike broke off I went to my local auto repair/body shop in Buena Park and they welded it back on. I am sure you have one near you. It was a dificult rebuild and weld, but it was one third of the cost of replacing that section of frame. Your repair is fairly simple.
Man... I ain't never changing my brake cable! Good luck with the repair, and another endorsement for Blue City.
If it is chrome-moly or any other form of steel beyond hi-ten I would highly recommend not having it welded by just anyone; chrome-moly and the other special alloys of steel found in bikes require specific fillers and heat control to prevent brittle welds.
I also would not recommend having any kind of bicycle tubing welded other than by an skilled tig welder due to the thin tubing being sensitive to both blow through and heat. Before the days of tig welding bicycles were brazed because the heat required to weld would damage the tubing.
Both places listed can fix it well you may also want to talk to Jesse at Comrade Cycles.