My favorite 11th essential is a creation by Anastasia Allison. It is a reusable, antimicrobial pee-rag for use in the outdoors, or anywhere, instead of TP.
I personally own 3, and they are lifesavers! I use them on day-hikes, backpacking, snowshoeing, at the beach, and even during work.
I’m a proud supporter and I know you will love them too. Check out the rotating assortment of designs available and see more here