If you can afford it, get a thick memory foam mattress topper and stick it on top of a cot. Heck, some big couch cushions covered by a thick blanket will work underneath, too. Even a stack of old blankets will be sufficient. (It's a bit iffy on a hard surface like the floor). You will have the softest, sturdiest bed you've ever used. As an added bonus, you can pretend you're eight years old and camping in the living room.