I am guessing this relates to your post about CRT on Sun. morning. I don't know where you are located, or if you have time today, but Target has some Disney princess dresses in their toy section, and usually Toys R Us and Party City carry them, and of course if you had a
Disney store nearby. Just an FYI if you wanted to have it before you leave instead of trying to scramble on your 1st day, and could be cheaper as well! You could also get crown, etc if you wanted .
If not as PP mentioned you could go to another park Sat evening (after AK if that is your plan for the day) if you have a hopper pass(MK probably had the most), or to Disney Springs if not. There will be a bus at AK you can get on for these, or back to hotel, and then go from there. The app listed above could help you know where your desired items would be available. The other option is to get one in MK first thing - I am guessing the Emporium is open on Main Street while you are waiting for welcome show, and then as soon as park opens and you head into Fantasyland, there is a shop right behind the castle across from brft. that has all princess items. Good luck! Enjoy CRT - very magical!