... you can always use a cereal box. (Two because the swatch I am unravelling is knit from two balls of yarn).
See, they even have a neat little yarn anchor! (Not the one on the right because my flatmate opened it upside down. You can still hook the yarn over the edge).
It's better if they have some cereal in to stop them tipping over. (Better still if there's more than a tiny bit in an open bag so you don't end up spilling your flatmate's favourite cereal all over the floor).
I wish I had a niddy noddy.