.....probably athermal IR protective welding glass, "Shade 10" may be the ticket (albeit a bit extreme for 2-way vision).
I'm not aware of any DOT window glass that will block out-going light from escaping the window(s) generated from inside the camper (say, when you turn the lights on in the camper at night).
We have mirror-like (called: flash-coating) windows on our Outfitter. It is very, very difficult to see anything inside the camper during daylight. However, like sunglasses, these windows are meant to allow someone INSIDE the camper to see outside (just like wearing shades) with minimal (not none) reflection off objects outside.
So, a pair of shades (or, vehicle windows) coated on both sides would be extremely unusual.
Good luck with it!
Cheers