Forgot to say, I want that poster as a bumper sticker. Bad.
Aha! You can get the t-shirt here!
http://www.zazzle.com/obama_more_cowbell_tshirt-235581555377244957
More t-shirts and posters and stickers — though not the usual bumper sticker shape...
http://www.cafepress.com/RichManAnon/6893676