Oh goodness-- I just realized you were asking about the particular thread, not specific recommendations. I remember reading a number of threads about mattresses and mattress toppers, and a quick google search brought up five or six. I've no idea which one you might have been specifically looking for.
They all seem to suggest the same alternatives, however-- ordering a custom mattress or topper from a company like Rocky Mountain Mattress or another manufacturer that is closer to you, purchasing a standard mattress and modifying the base with plywood or some other material to support it, or purchasing a standard mattress topper and cutting it to fit with an electric knife.
My husband and I have gotten so comfortable with our Tempur-Pedic mattress with the Ergo adjustable base in the last few months that we are not entirely sure what we're going to do when our Airstream arrives this summer! All I know is that it's probably going to involve the wedges we were using before we got the new bed, and a memory foam topper... maybe eventually a custom mattress. At least there do seem to be good options out there!