http://www.travelfashiongirl.com/how-to-keep-your-passport-safe-while-traveling/ I spent almost NINE years traveling the world full-time. This is how I kept my belongings safe and the lessons I learned from my first and ONLY time having something stolen while traveling.
These are all the anti-theft devices shown:
Travelon Bra Stash (grey): http://amzn.to/2G9nOwg
Eagle Creek Bra Stash (black): http://amzn.to/2G89bJl