Store in the freezer (wrap in parchment and store in a freezer ziplock bag).
Notes
The macros here are for the lower-carb option, using 1 cup of rice cereal. Using 2 cups of rice cereal has: Prot: 13g, Carbs: 20g (0g fiber, 2g sugar), Fat: 1g, Cal: 141. If you choose to use puffed grain cereal, I recommend toasting it first at 425F (218C) for about 5 minutes.