I managed to find a copy on Craigslist a couple weeks ago. Apparently DWR (Design Within Reach or whatever they are) produced posters - one side had DWR stuff on it throughout the US, with Jackson Center highlighted in red, and the other had the picture posted above. They are 25"x36".
Unfortunately he only had a few so he may be sold out by now. And yes I am very glad I got one.
I also did the "good son" thing and bought one for my parents.
Try a google search using the terms "site:craigslist.org airstream poster" to see if he has any more (I can't do the search for you right now). He told me he also sold them on eBay so watch there, too. Unfortunately I can't find his email address at the moment.
Edit: Oops, old thread. Sorry!