There is this one which can latch onto one of the side storage things. And its super cheap.
http://www.aliexpress.com/item/Garb...MlXJmMNDldKiOdWOlqumP-2WWHIKIA4du4aAkUX8P8HAQ

http://www.aliexpress.com/item/Garb...MlXJmMNDldKiOdWOlqumP-2WWHIKIA4du4aAkUX8P8HAQ