What do you mean by a "Disney Easter Egg"? A colored hard boiled egg? I doubt they sell them, I suspect WDW's hard boiled eggs come pre-shelled in a 5 gallon pail.
Anyway, if you are looking for decorated eggs. the Germany pavillion has hand painted eggs for sale. The "egg artist" amkes them. She is a very nice woman, Jutta something - her last name eludes me right now. the eggs do not come cheap (hah! thats like a joke). Chicen egg sized ones are on the order of $100. (last time I bought one, which was years ago) and she gets super busy around Christmas and has a back order waiting list for custom eggs.
-dave