If not used during lights off : beer flat,,,fabric.
Much tricksy'r if you want to run it stealth. (Sunny outside : lights off : ac running = tricky)
Tricky because there is mass exchanges happening on both sides.
Essentially you are building a light baffle/ labyrinth. Could be outside or inside.
Large enough to not restrict air, yet enough double backs, to trap light.
A plenum or a lung.
In that scenario I cannot imagine anything "compact"
Another alternative, is to mount the AC in a different location, and pipe the cold air in.