Guy here that provides 'Porta Poopers' for migrants working in the local fields, planting and harvesting truck farm products.
He has regular porta johns mounted on single axle tow behind trailers, usually 2, one for men and one for gals along with a hand washing station that is a galvanized water container with a spigot attached at the bottom and a container with paper towels attached to it and of course a covered galvanized waste container for the used towels.
He has about a dozen outfits like that and empties them at the local sanitation facility. He delivers them as needed to whatever field is being worked. I believe he pulls them with a normal 1/2 ton pickup truck as well. We call him the 'flush, fill and fragrance' man....lol
Trailers are low enough to access the porta poopers without additional steps. Have have lights and legal running gear as well.