Does. Lowes. Carry. A replacement 20 amp circuit breaker to replace a 20amp federal Pacific circuit breaker

Yes carry yours WITH YOU Look at how it mounts or ask electrician that now works there during the week

Breaker box

If not, Home Depot carries them.

I bought one there, limited stock

Probably, they carry most types of breakers.

Probably, some CBs are interchangeable. If not try a wholesale store.