Scribd : Hosts multiple community-uploaded versions of the 21 principles in PDF and readable online formats.
Many excellent translations are sold as EPUBs on:
The Dokkōdō ("The Way of Walking Alone") is a short text written by Miyamoto Musashi, the famed 17th‑century Japanese swordsman, poet, and philosopher, shortly before his death in 1645. It contains 21 concise precepts for life and conduct, distilled from the more extensive Book of Five Rings (Go Rin No Sho) and Musashi’s own experience. The Dokkōdō emphasizes self‑discipline, detachment, clarity of purpose, and simplicity — principles that have appealed to martial artists, business leaders, writers, and readers searching for practical stoicism.