I snapped a photo of this sticker in one of the restrooms at Ritual Coffee Roasters in San Francisco's Mission District. There used to be one just like it posted above a small hole in the wall in the other restroom. That sticker was removed though once the hole was patched to, er, block the camera's lens.
Link to a bigger image
I made it up last year, originally as a prank for the toilets on the (Burning Man) playa (hence the Bureau of Land Management logo).
Print em out yourself w/ the PDF here, or remix w/ the template file: Link