You are going to need to call Airstream or Inland RV for the placement. In most units a hole will need to be cut in the roof. In your unit there will not be an AC prewire, or a drain tube, so you will need to factor that in as well.
There is not a model that comes with an aluminum cover that I am aware of. One of the things you want to consider is AC unit height. The Duo Therm Penguin seems to be the choice for the low profile while maintaining a 13,500 BTU rating. It also has a 2 piece cover so you could paint the top silver if you wanted