There's really "no worries" if you leave anything at home when you come to Hawaii. ABC Stores have nearly everything a traveler could want, plus every sort of Hawaii souvenir you can think of. Not only are the stores well-stocked, but they're around every corner—and more plentiful than Starbucks in Waikiki.
ABC is a great place for midnight snacks and drinks. You can even pick up some aloha shirts, sunscreen, and postcards while you're at it.