DSG Holsters, a division of DSG Arms, has something for you guys who work out of vehicles all the time. It’s called the DSG Ranger Rack. You can run it inside or outside the door pocket as you prefer and is vertically adjustable. Fix it in place using the rubber bumpers on the belt clips, or just mount it straight to the side pocket (unless you’re in a pool car or have one of those sergeants who waxes apoplectic at vehicle mods). Each magazine is held in an individual mag carrier then screwed down to their Ranger Rack, so it should be relatively simple to adjust for preference and vehicle type.