Make a test light too, it makes sure you always Gang the connector correctly, and you can test them from a power source.
You can also make things like this, that work for whatever else you might want to run, cell phone, kids game console.
Make everything work off of a power pole, have power poles in all vehicles, no need for a rig runner in each one, quickly move the rig runner or just use a direct to battery cable. Or take your radio to the house or put it in another hams vehicle.