Interesting how different we all are. I long ago got rid of all mattresses in both my home and RV. I replaced them with what I consider comfortable... for just a fraction of the price... with an appropriate sized piece of foam (not memory) and put a mattress pad on it.
I would look at Sportsmobile's website and their online system for planning your own floor plan with only what you want. You could choose to make their gaucho or platform system to fit a standard twin size mattress... and then work from there to add what bathroom, kitchen and storage you want.
You didn't give us your location... or at least I don't know where "nope" is. But Sportsmobile has three locations: Texas, California, and Indiana.
