We bought a Zinus 10", INNER SPRING mattress through Amazon a couple of months ago. It's a short queen, and cost us about $300. It's great, supports the two of us, full-sized couple, like a hotel bed. It came rolled up in a box originally from China, unrolled like a lifeboat in front of our eyes inside the camper. No smell, and laid flat after one night. We're very happy with it. The struts underneath still lift the bed, but just barely. I can see needing a prop stick in a few years to hold it up. The thing weighs 80lbs.
Sadly, Amazon no longer lists this item, but shop around and you might find it. If you get to the Zinus website, watch their unrolling video.