Install the rear AC unit from a van into the bed of the pickup. That shouldn't be hard for a good AC shop. Locate a salvage yard donor van that has rear AC, and buy the used rear AC unit. They've been available for a long time. I had a 1977 Econoline van with rear AC. Then you wouldn't need an inverter, but you might need a bigger or second altenator to produce enough juice to power the 12-volt fan in that second AC unit.
If you order the second altenator as a factory option in your new truck, it would not cost much extra. And you wouldn't need to worry about correctly wiring and fusing and resisting an aftermarket altenator. For example, Ford F-250 and F-350 SRW diesel pickups have an option for dual altenators that put out a total of 357 amps (4,284 watts).
Grumpy ole man with over 50 years towing experience. Now my heaviest trailer is a 7,000-pound enclosed cargo trailer, RV is a 5,600 pound Skyline Nomad Joey 196S, and my tow vehicle is a 2012 F-150 EcoBoost SuperCrew.