I can't think of what they're called, but that's a commercial product made to fit between the mattress and box springs, and hang a shotgun on. Then the comforter covers it up. Basically flat steel straps with hanger hooks on the ends, connected together with another strap across the back, and coated with something to not scratch your gun. A guy could make something similar very easily.
Found it - called The Back Up. They make them for pistols too. My wife would shit down both legs if I put one on our bed. But she lives in a Condition White world.
Thanks! Definitely not paying $40 for that! But I will try and build my own