I would run a dedicated 12V wire from the interior fuse panel back to a plug for your power station. If you want the plug active when the ignition is on, you'll need to find a fuse that's hot when the ignition is on (which you can figure with a multimeter - but usually the cigarette lighter fuse will do the truck). It's pretty easy to run a hidden wire to the back if you pull up the door sill trim and then fish it through the B-pillar trim and the rear cargo area trim. You can then install a ground wire to a body bolt somewhere. I'd use at least 12 ga for this wire, maybe more depending on the amp draw of the fridge.
For my rig, I have a always-hot wire ran to the rear cargo area (tied into the power seat fuse with a fuse tap), and a Amazon power panel that has a 12V cigarette lighter plug and two QC USB plugs. It's switched on/off, which is pretty nice if you need to charge a phone/flashlight/radios/etc when the rig is parked and not running. I have it switched off except for when I'm charging something. I cut into the side panel plastic with a Dremel and then screwed the plate into the plastic. It's grounded to a bolt in the jack storage area. This was actually one of the first "mods" I did to the rig.
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