I had previously found a magnetic gun rack for the outside of vehicle. The kind you could lean a gun against while you put on a pack or boots. Can’t find the product again on the internets.
I have a ranch hand on the front so magnetic would be ideal. Guncady wasn’t the one I had in my que.

Couple at Midway. https://www.midwayusa.com/s?userSearchQuery=magnetic+gun+rack&userItemsPerPage=24

These were sold by Sinclair.
Look to be a little better made than some of the foam ones.
https://gripperbybauer.com/collections/firearms/products/the-gripper-caddy

I've got a magnetic one I've had forever called a "Stick-Up." It must predate the Internet as a Google search reveals nothing. Looking at it, I think it would be pretty simple to craft something similar out of a piece of lumber with v-notches cut in it and some magnetic strips.