Walgreens has alot of Disney themed merchandise. they had some really cute light up wands that were Christmas themed. I have also seen light up airplanes and the spinners, so check them out.
If you have a car on vacation you can also find some stuff at
Walmart and Target near the parks. Both stores have an area with Disney themed merchandise. Pick up your fan water bottles here for $5 instead of getting them at the park for $20.
I bring the glow sticks that I buy at the dollar (now $3) area in Target. They are 15 for $1 and my grandson loves to pass them out to other kids sitting near us during the fireworks.