Thats what I have for my pistol mounted high next to my bedroom window behind a curtain.Mount this to the bed rail on your side underneath, don't load one in the chamber since a kid wouldn't know how to rack it (A Pump or semi) or turn safety off and you're set for less than $15, its what I use,
https://www.amazon.com/Tac-Mag-Gun-Magnet-25-Rating/dp/B00LR454YU