The answer is ?!
It's not a grammar question at all: it's just a question of matching patterns. "Do" in the first pattern corresponds to "?" in the second pattern; "not" in the first pattern corresponds to "!" in the second.
"Don't" is "do" + "not", so what you need in the second pattern is "?" + "!", which is "?!".
Again: this has nothing to do with actual rules of grammar, spelling or punctuation. The words and punctuation marks are used here as abstract symbols, nothing more.