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
If price doesn't matter, I like the Kuiu gear. It was founded by one of the guys that started Sitka before they got bought out by Gore. I know a guy that lives out in Jackson Wy. and he swears by it for warmth and that's how I got started on it.
Hunted Carroll County over the weekend. Saw several small bucks and a really small doe on Saturday and let them all walk. Heard lots of shooting. Yesterday, sat in the stand all day. Once the rain stopped, the deer started to move and got a nice, mature doe to put in the freezer.