Lowes sells a breaker that will work in FPE panels. Only about 3 times the cost of other brands. Its sold under the name Federal pioneer and is approved as a replacement use.
I might even have a 2 pole 50 FPE in my storage room - used of course - I save them when I change them out. Never know when one might in handy
Sounds like you have the potential to market service changes in your area.
