Small Fiver

We downsized in 2004 from a 26' MH to a truck camper. We are both in our early 70's and it's a bit small plus climbing those steps, so we are considering the shortest 5th wheel available. I have a 2012 F250 Crew Cab, 6' bed e/w 6.2 gas.

Can anyone narrow my search and advise me of any manufacturers that offers small units? I am thinking 18'-20'. Thanks in advance.