I believe you can buy them in any of the WS giftshops. We bought ours in Mexico several years ago. My dd loved getting hers signed by the different CMs. I can't remember what the cost was tho. Not expensive tho.
I don't remember the cost, but I do know that it was less than $15. You can buy them at any non-food shop in World Showcase. If I had to say, I think that they were $12????