You are right about e-bay. You didn't mention which type of lock you are looking for-- flint or percussion or what era the rifle will represent. If
percussion, you can get a first rate, new lock from Track for around $70.00 or so. Flint is somewhat more, but given the importance of the lock to the gun, a used one might be a false economy. Anyway, just type
track of the wolf into your browser window--it's worth a look.