If you are unable to locate a serial number on your .22 rifle, chances are it was manufactured before 1968. Until that time, .22's were not required to have serial numbers.
You will have to find a book on Mossberg. AFAIK, there is no SN data for this model. Best you will be able to do is a range of years. I can tell you that it is post-war.
From what I can find out it was made by Mossberg and is the same as the Mossberg model 20 and 21.
Egunparts has some.
Various other websites list this as a Western Field brand sold at Montgomery Wards but manufactured by Mossberg (hence the M in the model number). The Mossberg model number is 402
Your rifle was made for Montgomery Ward stores by Mossberg, and is a Mossberg 346K. You can check with a gunsmith, or check the website for gunpartscorp (look under Mossberg). Havlinsales also stocks many Mossberg parts.
You might find a magazine for one at egunparts.
Need more information. I can find no reference to a Mossberg Model "410" rifle. Is it perhaps a .410 bore shotgun? Please describe your firearm more fully.
Your rifle which was a Mossberg model 320 which was made for Montgomery Wards(Western Field) was made from 1960-1980.Any firearm made prior to 1969 did not require a serial number by law.That may be the reason you cannot find one.
One can find a clip for a 22 caliber New Haven Mossberg rifle through local gun retailers. These pieces can also be found through gun classifieds and gun manufacturers.
Regrets- you probably WON'T find them. That rifle was made from 1928-1931. Gunpartscorp is sold out of used parts for that model. You can check with the Mossberg section on the rimfire central forum, or contact Havlin Sales through their website, but the rifle is simply too old, and made for too few years. Good luck in your search.
Can't find that model in the Mossberg line-up.
The gun is a semiautomatic .22 rifle made by Mossberg. Not much of an accessory market for that gun. What are you looking for? sales@countrygunsmith.net
Made for Coast to Coast Stores by Mossberg, it is a Model 479. gunpartscorp lists SOME used parts for your rifle on their website- check under Mossberg 479. Your rifle has been out of production for several years, so used parts may be your best shot (pun intended)