Highly unlikely you will find any. Getting them made will probably cost more than the shotgun is worth.
On line auctions, gun shops, gun shows, pawn shops.
There are some sources for Crescent shotgun parts, but it is very possible that parts will have to be repaired/made.
Where can you find parts for your Charles daily shotgun
I would try the numrich gun parts corp.They can be found on the web.
This shotgun was probably made by Crescent, so your local gunsmith can probably find one in his parts pile. Or, if there are no missing pieces, he can repair yours.
Typical Crescent single-barrel shotgun. I have a good supply of parts. firstname.lastname@example.org
Modle 101 1380 410 shotgun
It is a shotgun not a rifle- and Crescent was bought by Savage in 1931.
Auction sites, Shotgun News, gun shows, gun shops
Some Enders Royal Service shotguns are Crescent Model 60's marked with Shapleigh Hardware's trade name, but some were made by other manufacturers.