A company called
Runaway Campers makes a small camping trailer with no plumbing. We just had a discussion about them here a day or two ago.
Two sizes, roughly 4x8 and 6x8 interiors, they are empty boxes with RV doors and windows, maybe some insulation, maybe not (it is a plywood box). These are compact enough for hauling into the boonies, but this also means no stand-up room.
For stand-up room in a camper with no plumbing, consider the
Scout line from Aliner. This is not an empty box, it does have furnishings. A "park ready" package adds electrical and city water connections, but no waste tanks or fresh water storage, and so does not really turn it into the Ranger model. I think the Scout comes in one size only, the 12-foot box.
Another thought would be to talk to the manufacturers of molded fiberglass trailers who sell factory-direct, as a lot of their business is built to order, and at least one does special builds for an export market. Both Scamp and Casita build "standard" models without bathrooms (that space gets used for storage, seating, or bunks) so that the only plumbing is for the kitchen, and you might be able to order a build without the kitchen sink and water tanks.
If haven't looked as much into the other egg campers still made, suspect that some other manufacturers may offer models with features at the "Scout" level, or can build you one. Similarly, LivinLite might be persuaded to build a no-plumbing CampLite, but they sell through dealers, which makes custom builds more difficult.