#2
The white border surrounding the image in the poster leads me to believe that it's an art print, not a poster. That would mean that some artist made that and reproduced it as a print. Not sure if that's correct or not, but that might help you dig it up.

Googled things like "circular optical illusion poster" "optical illusion art print", and I found some cool stuff but nothing exactly the same. Here's a link to the best collection I could find.

http://www.zazzle.com/optical+illusions+posters