I know I've seen it at places like the Marketplace at BC. The little resort stores have it but I didn't see any at the restaurants or at the parks. That doesn't mean they don't have it, just that I didn't see any.
I wouldn't plan on having flavored water readily available in the parks You may want to pack a few of the flavor packets to use with plain bottled water--I love them!! Whomever came up with this idea is a genius in my book.