Yes they did exist, at least as an offered option in the sales literature, but I haven't ever seen one, much less pics or drawings in the literature of same. I have probably seen at least 50, either in person or in pics and have never seen one with that option installed. Basically they were apparently 24" x 61" "Youth Size" bunk beds, and occupied the space between the refrigerator
wall and the back wall. They "May" have put the refrigerator/icebox below them at the back of the trailer, as the wheel well gets in the way further forward.
There was one posted here that the owner had modified about a year ago. And there were a few pics. He built it for his 8 & 10 y.o. as I remember.
If you are looking for a Hunter, and have to have that option, I am afraid that you will be disappointed.