Oliver, Scamp, Casita, Bigfoot... I'm sure there are more. All are double wall, fiberglass bodies (think boat hull), and are better for 4 season use, as the tanks are internal (vs mounted under, like a traditional travel trailer, Jayco for example). They last longer, have better resale, are better thermally, you don't have to seal the roof, like on a traditional trailer. The negatives, are they are BIG $$$ (you could buy 2 traditional camper trailers of the same size), and because of the molded shell, no slide outs. That means less internal space (no slides), but they are better for 4 season use (cold/water).
I REALLY want a Big foot B25RQ (rear queen), but just like the Olivers, they're close to $100K (the thing doesn't even have a motor or transmission :-).
Escape and Cotes are players in that space as well. The shells will last indefinitely. Some interior stuff is superior to traditional TTs. Other stuff is the same.
All of those are budget busters for me. This is the route I took. Azdel walls inside and out, fibeglass skin and aluminum framing. No wood in the structure.