Light proofing a window A/C

I bought a cheap window A/C with the idea to back my tent up to the wall with the A/C and seal it to the window/wall. However, I find that daylight comes through the A/C case louvers, through the Styrofoam fan housing, and out the cold air vents. I don't want to alter the outside of the A/C. Any ideas on how to make a light trap to fit over the cold air vent without restricting the air flow or blocking the electronic controls that are located just below the vent?

I would say alum foil or more ideally fiberglass duct board, and alum tape.