Pickup bed "sleeper"?

[Route66Clare]

I have been doing some casual searching of the net for a small cab extender so that I can hall the whole familhy on trip, not just three of us. I have come up with something called a walk-in "Sleeper". I'm wondering if anyone here uses one on their truck or has modified/created their own? Ideally I would like to take the back end of a truck cab, all the way down to the bottom of the cab and up to the front of the window (so a 1960-63 so it slants the right way) but I don't have the money or the experience for that...any info would be great! Thanks, Jason