Probably only from Winnebago.
The mattress like all RVs are terrible.
We use a double bed softer mattress from the house.
Before that we had a 3" memory foam bought online from Walmart, I cut the corner out of it. But it would not stay in place.
A double bed mattress slightly interferes with the door closing. I removed the bathroom door since we are married.
2015 Fleetwood Discovery 40E on a Freightliner XCS chassis with a Cummins ISL9 pulling 1 and/or 2 motorcycles, '07 Honda Accord OR a 17' Runabout Boat.