There are many options out there. Example:
https://tandyleather.com/products/moccasin-pattern-pack
https://www.amazon.com/Tandy-Leather-Moccasin-Pattern-62668-00/dp/B011M48ENM
https://www.springfieldleather.com/Pattern-Adult-Moccasins_3
https://www.instructables.com/DIY-MOCCASIN/