You may want to start with Numrich gun parts corp.They can be found on the web.
Try egunparts.com, gun shop, gun show, pawn shop
brownells
Gun show, gun shop, internet, newspaper.
Try www.Gunbroker.com. They are no longer produced.
You can start your search at browning themselves,if you have no luck you may want to go to numrich gun parts corp.
Where can I buy a forend grip for a wm Parkhurst double barrel 12 gauge
Will be hard to find, and expensive. Do an internet search for Corson's Barrels.
Pawn shop, gun show, want ad, gun shop
You should be able to find a list of gun shops in your area that may have a Browning shotgun of this make.If you do not,I would go to gun broker.com.I believe that they will list a few of this model from time to time.
16364757300 Midwest gun works. $40.00. Mine broke too.
Gun shop, pawn shop, want ad, for sale ad, hunter, collector.
Google a company called Polywad. I have bought shells from them and was satisfied with their product.