I have read that the old style round Theo Bargman breakaway switch is unavailable. I haven't seen a thread on fixing them here either. I do have a solution if you want to keep the old style you have. If your switch isn't totally rusted out or smashed, it can be repaired. The inner workings are a very simple design. Don't toss it out ! I can fix it or I can tell you how to do yours. I fixed mine for 50 cents. Now thats cheap
If you use stainless screws that will put the repair costs at about roughly 2 bucks I would think.
The Finished Product