As far as ammo. Tungsten shot hits like a truck. Should make a 410 an ethical turkey gun out to 40-45 yards. I used Apex Ammunition in 12 and 20 gauge when I had a place to turkey hunt and it was devastating.
Bass Pro site says they have some in Arundel Mills. $600.00 there. https://www.basspro.com/shop/en/tristar-viper-g2-turkey-semi-auto-shotgun-with-pistol-grip-in-truetimber-strata
Semi-auto, camo, with a pistol grip. https://www.cheaperthandirt.com/tristar-viper-g2-turkey-.410-bore-semi-auto-shotgun-24-barrel-3-chamber-5-rounds-fiber-optic-front-sight-synthetic-pistol-grip-stock-mossy-oak-obsession-finish/FC-713780975825.html
looks like a standard weaver style mount for a benelli shotgun to me https://www.mountsplus.com/weaver-93a-top-mount-base-48506-for-benelli-super-black-eagle.html