Go to Tickerfactory and create one. To add it you cut and past the <usually it's an URL> to the bottom of your post, I think you can also set it up as a Signature.
But you have to first post here a set number of times before it will allow you to use it. I'm on post #11 and it won't let me yet, so I don't know what that minimum number of posts actually is.
Sheri