Yes they sell in park. They also sell now in the parks the cooling towels. However here are my cons of the disney spray bottle/fans so you are aware. I took some pics of one of ours so you get an idea of the issues and size.
1. The lanyard has "sharp" edges of velcro where it rests on your neck. -
Not painful but really annoying, and gets more annoying as the day goes by, and even annoyinger as it gets hotter(which is when you eed it) so maybe wrap that part in some cloth or medical tape or something.
2. The little fill cap tends to leak. -
So be aware of this, you don't want to be like me and have it hanging on your neck, resting in your lap on a ride, only to realize after you get off the ride that it looks like you pee'd your pants. I was going to try some silicone or something(on my "to do someday" list)
3. Its kind of heavy when full. -
Not super heavy but it becomes an albatross around your neck adter an hour or so. I just left it half to 1/4 full and refilled as needed at drinking fountains/starbucks.
FYI,
If you are staying offsite and are near a CVS/Rite Aid etc may want to check in there fir a cheaper and smaller one.