Several different companies made shotguns for Wards. First determine what it really is (look in a Gun Values book and compare the gun to the pictures) then go to gunpartscorp.com for parts.
THESE WERE MADE BY H & R IN THE 1960 ERA
Without further information, anywhere from the 1930's-1970's.
My father used a Wards Western Field 410 gauge repeater as a young man. The gun I believe is approximately 70-80 years old. If you have a patent number you can contact the pantent office and they should be able to tell you when the shotgun was first produced.
I have a 16 gauge double barrel for sale.
The model number of your Wards Western Field.
This should be a Mossberg 500 in a Montgomery Wards suit. Check any dealer for the availability of a slug barrel.
I would guess it was made by Stevens.
1934 - 1940 they were made.
It's a Stevens 620.
Mossberg
A Wards Western Field Model 41 is a 22-caliber rifle. It was actually manufactured by Mossberg, but intended for Wards. Manufacturing took place primarily from 1935 to 1939.
Savage Fire Arms Company for Montgomery Wards