Look in children's magazines. Magazines like 'Highlights for Children' often feature short Christmas stories during the holiday season. Also, some bookstores have special collections of short stories for kids at Christmas. You can ask the staff there to point you to the right section.
Many websites dedicated to children's stories are good sources. For example, Storyberries has a variety of short and sweet Christmas stories for children. Additionally, you can check out your school or local community library's website. Sometimes they have digital collections of short Christmas stories available for borrowing or reading online.
You can find short children's Christmas stories in local libraries. They usually have a section dedicated to children's literature, including Christmas - themed stories. Another great place is online platforms like Project Gutenberg, which offers a wide range of free e - books, many of which are short children's Christmas stories.