What store do you buy potash alum from?

99 cents store

AnswerWikipedia says this is an astringent, styptic (stops bleeding), antiseptic, natural deodorant, and an ingredient in traditional Chinese medicine. So...try a Chinese grocery store or a health food store.

You can buy Alum in any grocery store in the spice section. It usually comes in the tiny spice containers and is used for canning, such as pickles. It is also very cheap.