I can understand wanting to save a buck, but if you are going to 'slum' it I don't see why you'd bring an air mattress, etc. If 'quality' sleep is that important to you, spend the extra few bucks and sleep in your own bed!
I do have a good example of a lock you can use while sleeping at the airport, these wire locks are light and simple and you canloop them through zippers, etc to really secure your stuff. There are some slightly cheaper models out there too
http://preparedness.com/lewnclartrav.html