I know, anyone can install a fire extinguisher.......
But, after seeing a pic posted by kaiser67
about something else, I noticed he had an extinguisher in the driver side rear door panel, inside the useless angled "drink holder" or whatever GM wants to call it.
I tried a couple throwaway Kidde extinguishers in my truck but they were too big in diameter and it seemed like they would eventually cause the door panel to stretch, break, separate, or whatever.
I PM'd kaiser67
and he told me the brand and model extinguisher he used.
After finding an Amerex dealer, I bought an Amerex B417 which is a 2.5 pound ABC extinguisher for about $30.
This extinguisher is all metal, including the operating mechanism, and the included mounting bracket. It's also refillable.
I did remove the hole bracket for hanging it on a wall (one screw) and I trimmed down the lower aluminum handle so there's no chance of it rubbing on the door panel above the speaker grill.
The extinguisher fits snugly in the pocket and doesn't rattle. It's also easily accessible.
This is more than just screwing in a bracket somewhere, but after downsizing from a Sierra, I'm finding it tough to get all my stuff in this truck without just throwing it under the rear seat.