Last time I checked K-Mart was out of the gun business. Big 5 carries shotguns and often has good sales, I just bought a Mossberg 500 2 barrel combo (18.5 and 28) for $219.
Wally Mart is polically sensitive and sells such things only in politically accepting areas. The Wally Mart near my office in San Leandro, CA doesn't handle such offensive items, but the one fifteen minutes away handles a limited range of politically incorrect items.
I purchased ammunition and saw rifles, but can't remember if they had shotguns. It was in the Union City / Fremont area. I think it is off the Alvarado Niles exit.