I found where I got it :) Over at The Techy Teacher, she posted this idea, and my kids finished it up today during groups. They came out really cute, and after I showed them some pictures of the Milky Way, I had a few want to add spiraling galaxies. I also saw some aliens too, and since we are in the midst of testing a few added "Beat the State" slogans to their posters.
(this cutie up top asked me if she could stop modeling after I had taken the picture)
(see the aforementioned aliens in the little boy's picture above)