John, Here's a link to a plan for a simple chair;
http://www.valleystargazers.com/Chair.pdf I think it's the one mike built, If that doesn't suit your needs there are countless more pics and plands out there if you do a google search for observing chair plans. I like the look of this one which would be fairly easy to copy from the pix.
http://www.catseyecollimation.com/cperch1.html 