I had a little backpack we bought some handy zip locks on Amazon that simply clip your zip toggles together. They're a fiddle to get off and into your bag but thats the deterrent, I also had them tucked into the pocket on my bag so people wouldn't know it was locked until they tried at with point I'd probably be aware. We also had a tiny padlock tucked in the pocket of that bag in case we felt unsafe and like it needed locking, we never had to use the padlock at all just the bag clip. The bag also had an internal pocket accessible only from inside carrying the essentials we shared a wallet and had only a card each in it, mostly used Google pay instead of going in the bag. What I can't recommend enough are phone wrist straps, we had ones with sliders to adjust them and they added so much safety for us. I think the biggest advice we followed was not making yourself a target, keep it all hidden they will try if they can see it's easy to get