They're limited to Japan, but are usually given out through Silver Peels, which are like scratch offs, except you use sticky tape to peel off the silver instead of scratching. Usually you have a task to complete on the card (like find 3 of a specific Kanji in X amount of tries) while totally not using a flashlight to cheat and if you complete the game successfully, you mail it in to the specified address for a chance to win. At the end of the campaign, they pick 100 lucky winners to receive the kit. As mentioned above though, these aren't accessible outside of Japan, and so far as I know, no deputy services handle this sort of thing (even those who handle in-store orders).
I shorten the names to CoroCoro 100 or 100 Limited for convenience, but it means that only 100 are distributed through the campaign. They sometimes reappear through other avenues, such as Death Rex Purple Dragon Form being sold through Shogakukan's mail-order site and a Normal!Wild Liger version of the Guren being sold at the World Hobby Fair. This is pretty rare, though.