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.
Sears 200 series = Winchester 1200. Parts should be available from e-gunparts.com if you can't find them locally.
Typical Crescent single-barrel shotgun. I have a good supply of parts. sales@countrygunsmith.net
My cross reference list indicates that this is a Savage 59. If your local gunsmith can't find the parts, you can check with www.e-gunparts.com
Parts for these shotguns are hard to find. EAA Corp carries parts for Baikal shotguns. A good gunsmith might also be able to help make some parts.
Go to"krieghoff.com".
try: gun-parts.com
You could try Gun Parts Corporation.
You can't... you will have to make them yourself or have a machine shop make the parts
Some of the larger used parts dealers may have a small quantity. Try www.e-gunparts.com or Jack First Gun Shop.
These single-barrel Crescent shotguns range from < $50 as a parts gun, to maybe $100 if in excellent shape.
try: gun-parts.com
Need more info. Which manufacturer & which model??