Gun shops, gun shows, internet auction sites such as gunbroker, auctionarms, gunsamerica. I did check a couple of my gun parts sites, and they have none, or have sold out.
Try http://www.canadiangunnutz.com/
You can get a clip or magazine for a 20 gauge model 228 Kessler shotgun from one of several gun parts catalogs. These include Cheaper Than Dirt and the Numrich catalog.
Try gun shops, gun shows, want ads, for sale ads, pawn shops, garage sales, estate sales, on line auctions, Shotgun News, MidWay USA, Brownell's, egunparts.
1951-1953
50-100
You will need tihe services of a good gunsmith
In good shape the most is $120.
Kessler. Only in business from 1951 to 1953.
i had one it valued at $73.57 want to sell it
50-60 yrs old. 50-150 USD
Kessler, Silver Creek, NY, 1951-53. Valued at $35 to $90 according to the Blue Book.
Need model number