there is the Stevens side by side shotgun model 311
First try the local gunsmiths. Check at a few gunshows if there are any in your neighborhood. You might try Numrich Gunparts.
I don't find the Westernfield 530A but be careful: there is a Stevens 530 (1912 to 1918) that is a pump shotgun as well as the Stevens mod 530 (1935 to 1952) double barrel.
Jack First Gun Parts. Search the web, they have a web site with the phone number. They do not have a catalog on line.
There are some sources for Crescent shotgun parts, but it is very possible that parts will have to be repaired/made.
I too have a Ranger .410 sxs hamerless shotgun. I believe it to be made by Stevens. Possibly a model 311.
If it is side-by-side, probably Stevens.
I can say that the Stevens model 311 side by side shotgun was discontinued in 1989.I would go to the Savage arms web site,they may be able to help you find out when the manufacture of your shotgun was started.