Kind of unique but they are certainly out there.
The "Eyes on Design" event has had a few displays on vintage camp trailers (aka the "Tin Can Tourists"
and there are usually a couple specialty built rigs, including some from Pierce Arrow and Duesenberg. The rig pictured below is particularly notable because it uses aero frame technology and is covered with a "fabric" like naugahyde.
It's not out of the question, since the 5th wheel configuration was invented by Detroit blacksmith August Fruehauf in the early 1900s, in true Michigander fashion, so that he could safely tow his boats "up north".