Cash in a pocket
I adopted this habit when I was traveling. I am uncomfortable opening my wallet in public. It's easy for anybody to grab it and run with it, but even easier it is to accidentally lose a card, a note, or an ID.
I always put the cash into my pocket. It's usually as much as I will need during a day. It is so great I keep doing that even when I'm not traveling. All I need to have with me is a phone and cash, in case cards are not accepted.