Years ago I had a quadlock and it worked fine. Secure, well made, yada yada yada.
In the many years since, I have exclusively used a jersey pocket because it is less expensive, just as secure, and just as well made. It is actually designed specifically to hold things like a phone. Truthfully, I have a zip pouch wallet that holds money, ID, and the phone.
I do have a cheap $6 phone holder for my indoor trainer bike's handlebars. Easy access to ZWIFT controls and music. Its like the one tkamd posted- rubber bands all around and its secure.