I doubt there is a kitchen in the western world that doesn't have more than one clip to reseal bags such as chips or cereal, in order to keep them from going stale before they are consumed.
We have a number of clips designed specifically, and while they are not terribly expensive, they do cost money. I have also used clothes pins and bulldog clips designed for holding bundles of paper together.
But here is something my husband came up with that works like a charm and costs absolutely nothing. I am sure most people refuse to take the free plastic hangers that come with clothes bought in most of the major stores, but next time you buy a skirt on a hanger like this, ask to keep the hanger and cut the clips off, the remains is recyclable and the clips are great for resealing bags.