Looking for the best inflatable mattress for camping?

My wife and I usually camp in October / November time frame in the northern coast of California. Most of the air mattress' we have used loose a lot of air through the night. To the point where our backsides are easily on the floor while our heads are 7 inches of of the ground. I know that with the cold weather we are bound to loose air, but i was curious if there are any recommended air mattress' out there designed to stay better insulated or something. We tent camp so it will not be for indoor use. We do not want to get the thermoRest ones from REI because they are at least 100 a piece. Thanks