You could try Gun Parts Corporation.
gunpartscorp.com
Exploded Firearms Books (soft cover) Editions 1 & 2 both have parts diagrams for this rifle and many other rifles,shotguns and pistols.
Most automobile dealerships will give you a vehicle parts list and diagrams. Many auto-parts stores will get you the parts lists and diagrams.
chrlesdaly.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.
You can obtain 1995 Acura diagrams at most Acura dealerships. You can find the diagrams at most auto-parts stores. Many auto-parts stores will print the diagrams off for free.
You can find parts for many westernfield shotguns at Numrich gun parts. WWW.e-gunparts.com
You can find it on manufacture websites.
You can find a parts diagram, for your Toyota automobile, at most Toyota dealerships. You can also find the parts diagram at most auto-parts stores.
Honda diagrams for a 2007 Honda Accord are available through parts stores. Another place to find these diagrams are in the service manuals made for these specific cars.
The Sears 200 series = Winchester 1200. Parts should be available from e-gunparts.com if you can't find them locally.
You might try e-gunparts.com