I went to the one in Grapevine and they didn't have it. So we went to another store, but I can't remember which city. Somewhere in North Texas. We went inside. I tried multiple times to get the item from the Nintendo Zone App. We had to call a guy over who had no idea how. Then we had to call the manager, and they didn't know how. Finally, we called the best game geek in the store and he didn't know how. By then it had been an hour and we were getting ready to leave from being annoyed so much. I told them to wait and I tried something else. I entered the best buy wifi connection on my 3DS. Then I went inside the game and to the post office. I got the item, saved, and logged off. The whole store changed the directions on how to get DLC items just because I figured it out. Yeah, that's how smart I am. Anyone want to judge me now? Didn't think so.
EDIT: So basically, go to a store where there's a physical Nintendo Zone electronic thing in the video game area. Then ask them to provide you with the store wifi code, which the AC:NL site conveniently left that part out. Then you'll be able to get it at the post office. And the store locator is messed up too.
@Ben NYC and Keybug: Nintendo zones work. There's no need to use your phone for it, UNLESS you don't have any nintendo zones in your area. You're lucky if that works. The nintendo zone app doesn't work for me, even when I'm at the Nintendo zone.