We've owed a pop-up and are on our second hybrid. The mattresses in these things to us are not much different than the air mattresses we used when tenting. As said above, just throw a sleeping bag up there. We use a single sleeping bag laid out flat, pillows, and light weight comforters. All of three minutes to "make" the bed.
2013 Jayco Jayfeather X20 E (sold)
2016 Chevy Silverado LTZ 2 Z71 Crew Cab (sold, and dearly missed)