Any mechanical camera--35mm compact rangefinders, 120 folders, even a Minox B would be a good choice.
Some thoughts: in 35mm, you can bulk load short rolls so it doesn't have to stay around forever waiting for you to finish the roll; likewise for 120 6x6 or 6x9.
Don't keep in in the glove box, though. The heat build up will get it too hot. Use traditional black & white film. FP4+ or HP5+ would be OK choices in 35mm or 120; for Minox, go for the 100-125 speed film that is available.
All of my flying saucer photographs are made with a Retina 1a or a lla loaded with Tri X. I am very fond of the 1a even though it has no RF. Most all of my "saucer" shots have been more than fifty feet away, so no problemo.
It would have to be a fully mechanical d******l camera that doesn't need batteries!
Even the most casual reader of "The Area 51 Tribune" knows that battery-free digital cameras are among the most common of alien technologies. Well known since the Fifties. Of course, the bigwigs at Ever-ready and Duracell have pressured the government to keep it buried.
That is called grain. It is supposed to be there.