I purchused
this projector and
this 16:9 Matte projection screen for outdoor movie nights. We use a JVC portable bluetooth speaker for sound.
I attached heavy duty velcro Command strips to the back of the screen and it secures nicely on entry (passenger) side of the trailer.
Screen, Velcro, and Projector were all less than $200. Just looked at current prices. Now about $150.
Don't expect indoor theater quality. The projector upconverts to 1080p. But for a campground, it works wonderful. As a matter of fact, using it tonight for the kids in the campground.