Open trailer

I would buy a heavier style utility trailer that has 2 x 4 stake pockets. Then, you can add 2 x 4s and OSB or plywood sides. You could also easily put other items in that type trailer. I’ve used my custom 5 x 10 open trailer that way. In my case, I’ve also put some items under tarps and strapped them down. That also prevents people from taking a look at what you have back there.

in case you are wondering, I made it 5 x 10 to have less wind resistance behind my Explorer. It is harder to see behind the camper.