Interesting re your bag...I have debated getting something similar for when I travel to NZ but up to now done nothing about it...was particularly watchful in Rome this year among all the crowds, would give peace of mind. Your arms aren’t long enough!
This is the backpack I have: https://www.travelonbags.com/anti-theft/type/backpacks-slings/anti-theft-classic-backpack-842