I think you'll find that about the minimum BTU they bother making is
5000.
My 5500 BTU GE unit cooled my Westy just fine on days when it was 110
(but Westy parked in the shade).
Unit cost was about $140.00 but US Made GE Product.
Weight about 50 pounds, light enough to pack around and hang on the
window.
Unit weight was always my specification since most campgrounds that have
Electric you can suck 100 amps for the price of 5 amps like the giant
motor homes.
There might be a rare situation when you want to rent a generator to run
the unit so keep that in mind.

Stan Wilder