I have a used Select Comfort Twin XL (38" x 80") mattress with a traditional cover, wired toggle firmness control, foundation, and frame. It is equivalent to a Sleep Number 3000.
So, basically, it's an air mattress surrounded by some foam and a shell.
I've been the only person to use this mattress, and it has some discoloration due to dyes leached from the bedsheets and sweat (but that's it, I promise). There is some wear on the foundation shroud (you can thank our cat for that).
I don't think it leaks at all, but it definitely gets "deflated" in colder weather.
I'm not really certain what I'm willing to trade for it. Make me an offer if you're interested. I also have some unopened twin extra-long jersey sheet sets that I'd be willing to hand over with the bed.
The bed assembly is located in Ashland, NH. The prospective owner (should one be found here) will have to come pick it up.
If you have any questions, please do not hesitate to ask.