Even better is you can purchase a popcorn bucket. Sure they cost around $12 but they are always adorable and make a great souvenir that I use the entire trip.
I purchase a bucket the first day and every trip to purchase more popcorn I purchase the typical serving and dump into my bucket. That means I get to keep my popcorn safe while on rides.
I don't usually buy more than 1 but I found 2 different buckets this past trip - Lightening McQueen and R2-D2.