FPE or Push-matic? TWo seperate entities in my mind...
FPE only made one of common company style stab and bolt on.
When I think of Push-matic Bull-dog's they were not of the same brand, or style. Haven't seen one in some time - not frequenting that type of work lately. If thier were the demo drew removed them long before I get there.
FPE, my supply house carries one of two companies that manufacture replacement breakers for the US market. (Still pricey - it pays to remove most often)
For Bull-dog Push-matic, I get used ones from a local re-seller that tests and refurbishes them.
The same for certain FPE. But the same thing, why not rip it out and start over? The breaker cost is justification alone. If that doesn't justify it, I can get replacement panel parts from a scavenger shop a few (60) miles away.