You can find the egg on Amazon and Etsy. The only difference is that on Amazon a black egg turns pink and a purple egg turns blue. If you don't even want that much of a hint, the Etsy eggs start black for either gender.
How do you find out if it was a prince or princess that was promised? Heat it up! The eggs are metal with color changing paint.
What else do you need for the perfect "Game of Thrones" gender reveal? A "Baby is Coming" banner is sure to let all of Westeros know about your little arrival.
You can even get "Game of Thrones" themed cookies from The Cookie Pirate in Houston.