The autism society has stuff like that (so we don't have to take the time to explain what are kids are doing having a meltdown in target!), but I have to admit that I didn't find them all that handy.
I never could dig one out when I needed it.
However, I keep a pen and post-it notes in my purse and always am able to scribble down www.birthmark.org
when I run into a kid with a birthmark.