Here's the one I made.
http://www.outdoorsmenforum.ca/showthread.php?t=24357
I like the idea of the style you mentioned, and I designed one about 6 or 7 years ago, but I lost my AutoCAD file I had for drafting it.
I might be interested in doing up some plans for you (for free) if you want to incorporate what features you'd like.
I work for an architect, so I have access to drafting software fairly easily. I find that half the fun of these projects is planning them. I'd find it a fun little activity to design what you're looking for.