Bleg — Button, Button, Whose Got One?

After Yuri’s Night  passed, I needed something to fill the gap on the top part of my right sidebar. I sorta-kinda stole the image there and made a link to the Planetary Society’s “Save Our Science” campaign.

I’d like to rotate it with another button, but I can’t seem to find a good  geek activism link, preferably with a pre-made button. If anyone could suggest one, I’d appreciate it.