Just purchased a SereneLife portae AC unit for my 2280. Cheaper than a rooftop unit and WAY easier to install.
Just set it on the floor and stick the vent hose at one of the bunk windows and zip the inside flap closed on it.
Works well in my Popup and cools it down nicely.
This unit a somewhat noisy but the wife and I seem to sleep better with white noise, so this checks off 2 boxes.
See attached pictures for location.