I have had a number of things plugged into the 12v accessory port in the boot. Over time the female receptacle has loosened in the sidewall to the point where I have to remove the access panel and reach in and hold the receptacle with my hand when I plug in an 12v adapter. If I don't, the whole receptacle will push through into the cavity between the sidewall and the fender.

Has anyone figured out a way to secure this receptacle to the sidewall? The OEM part seems flimsy at best.....

 

You could epoxy it in place on the back side. It will be plenty secure but will be harder to replace it the need ever arises although I personally have never had one fail. I have epoxied my front one in place for the same reason, flimsy mount.

 

Here is what I would do:

Pick up a piece of aluminum or metal from a hardware or auto parts store that is relatively thin but strong enough to provide a sturdy mounting point. Drill a hole that is the appropriate size that the accessory port can slide through the metal and be fixed to the metal so that it is sturdy. Take off the rear plastic panel and affix the piece of metal inside the plastic, attaching with velcro, tape, glue or whatever else you feel will make it stay. Then reassemble everything and when you install the accessory port into the metal the lip of the accessory port should cover up the metal underneath and your problem should be solved.