I have seen a vertical vehicular mount that held the mag against the lower portion of the onsole in the front seat. The muzzle did not point straight up, but was angled out the front window. The mount had a plastic "shield" that covered the trigger and mag release.
The clamp was a tradional key style, with two padded "c"s that surrounded the foregrip (roundstyle).
I'm not sure who made the mount, and I'm not even sure which department was using them. Off the top of my head it may have been Las Vegas PD or the appropriate county SD that has jurisdiction in LV.
I don't think that there was any protection against manipulating the charging handle, but I might be wrong about that.