It should only cost a few dollars if it only needs the firing pin replaced. Your shotgun is only worth $50-$75 as a shooter (but have the gunsmith verify that it is safe) and about the same as a decorator (wouldn't need the firing pin anyway). So, economically, it's probably not worth the expense.
The American arms regulator was manufactored by Uberti. There are numerouse placesonline where you can purchase parts. the current version of the gun is the cattleman
Try gun shows, Shotgun News, Gun List, local gun shops.
Go to Numrich Arms website, you can see a parts list and purchase a parts diagram for about anything- www.gunpartscorp.com
it is a Stevens, parts are interchangeable...
Gun Broker, Auction Arms, American Arms
Numrich Arms, Internet or Make Them.
probably
No public records
Numrich Arms has parts for the 311
Franchi
try gunstock inc. they have them
Try Numrich Arms. They go by gunpartscorp.com. They have some parts, some are unavailable or expensive for this low value shotgun.