It may and often is be impossible to find parts for your particular gun, But many of the makers used alike or very close lock parts and trigger sets. Short of finding a donor gun, check out Dixie gun works for lock and trigger parts, and auctionarms.com and gunbroker.com for donor or parts guns.
Not readily. You'll find that parts will need to repaired or made by a gunsmith.
There are some sources for Crescent shotgun parts, but it is very possible that parts will have to be repaired/made.
Jack First Gun Parts. Search the web, they have a web site with the phone number. They do not have a catalog on line.
Numrich Arms has parts for the 311
Ejector and firing pin springs and parts
Where can i find info on a Reno Shotgun
You might try e-gunparts.com
Need a detailed description of ALL markings.its a side by side shotgun it was made by thomas bland the number is 15550.
I have a Robinson side by side shotgun12g is it a English gun, and what is the price ?
If they are straight pins I would get some drill rod or pin stock down at the hardware store, put the pin stock in an electric drill mounted in a bench vise & file the pin stock down to the proper diameter. Use the drill as a lathe. Or, See if you can find your model shotgun on the Numrich gun parts website. They'll charge you an arm & leg but they might have the parts.
Try gun shops, gun shows, want ads.
Take the forearm off, it's usually on the bottom of the barrels.