ive known about the cereal ones for some time, i use old modelcar boxes for mine as i dont eat that much cereal.
ill add my own tip if youre cool with it
instead of reeking up the whole house with the smell of filler to patch one low spot on a kit i use a syringe filled with putty and disperse a dime at a time so that way i dont over mix or make a mess. i mix all my putty in a pringles or flexible cookie lid.