This is non-standard but here is what I did in my PUP days.
I removed one Propane tank (I only used one at a time anyway) and cut a hole in the front of the unit.. Mounted the window A/C on the propane tray and in the hole..
Now on a canvas PUP this is not going to make a lot of cool, but it will suck a lot of HUMID out of the air and that is a good thing.
Some PUP's have a strong enough roof to support a roof mount, this would be better.. but I truthfully do not recommend it.
Home is where I park it!