New for Halloween 2019: Addams Family Animated Movie costumes (via Amazon). They're based on the upcoming movie which comes out on October 11, 2019.
For the Morticia Addams costume, the wig is sold separately. The Gomez costume comes with the half mask; the Pugsley costume comes with his half mask and an attached belly that most American schoolchildren wouldn't actually need to make the costume work; the Lurch and Fester costumes come with a half mask; and you'll need to buy the Wednesday Addams wig separately.
If you prefer to come up with your own costumes, the creepy Addams Family Animated Movie half masks can be purchased separately. Here's the Pugsley half mask (via Amazon).