Use a blow up air raft, the kind used to float in a pool, as a bed when camping. The air raft carries flat and, when folded, it makes a small package. It is lightweight and it can be used as a float near the campsite if you are camping near water, so it is double duty. A large bath towel placed on top of the air mattress will keep silky type sleeping bags from slipping off the top of it.
You will be thankful you toted along that air raft when you lie down to sleep. The inflated air raft will be way more comfortable than the hard ground, and it's cheap. Some stores sell air rafts for $1.00!