I recommend the Camelbak Antidote Reservoir. The closure is really easy to use and there's a handle where you can hold the opening to fill up the bag. It's super easy to get in and out of the water refill station because it only takes like 5 seconds to open and close the bag.
My friends have the bag were you have to slide a piece of plastic into something to securely close it. It may require two people: one to hold the bag and one to close it.