I'm looking for a portable a/c unit I can plug into my truck.

They don't work very well since they have the hot parts too close to the cold parts inside a small case and they have little airflow. ANY small window unit will be MUCH more effective and use half of the electrical power. There are drivers that have a plywood board they put in the passanger side window once they get parked and keep the cab/sleeper cool.

This is what it looks like after they get parked, not while they drive.
https://external-content.duckduckgo...a597e88a485111999a6e4374558988ac79&ipo=images

 

Really comes down to how much you want to spend. A lot of drivers are putting 120v mini splits in their sleepers (home units).
I've been doing extensive research recently and found that 12v cooling systems are far more efficient but haven't progressed as far as 120v systems (not so many options & prices are higher). 120v runs directly from the batteries via a 3000 watt inverter. 12v is the same but are designed to be used & charged by a .

 

The small window ac's pull 800 watts peak. 300 watts continuous.

A 1000 watt inverter should be just fine. Or get a generator.

 

Snowwy's info is correct with slight variances depending on the manufacturer. His/her info is based on a 5000 btu window unit.
Consider getting a capacitor also, $20.