I use one of those running bands to secure my phone, but it goes on your wrist. It’s great.

VUP Wristband Phone Holder for VUP wristband for phone

https://smile.amazon.com/CarryAround-Coffee-Drink-Carrier-Holder/dp/B00UJD3D2K/ref=sr_1_7?dchild=1&keywords=drink+carrier&qid=1592335658&sr=8-7

https://smile.amazon.com/Coleman-30-Can-Insulated-24-Hour-Retention/dp/B019YDUTBS/ref=sr_1_24?dchild=1&keywords=small%2Bcooler&qid=1592335682&sr=8-24&th=1&psc=1

and this

https://smile.amazon.com/VUP-Wristband-Samsung-Rotatable-Walking/dp/B06XSZ375C/ref=sr_1_3?dchild=1&keywords=wrist+phone&qid=1592335770&sr=8-3

Deeper has the phone mount for fishing rod, it works. And you also have lots of ways to mount phones, such as armbands and wristbands. https://www.amazon.com/VUP-Wristband-Samsung-Rotatable-Walking/dp/B06XSZ375C?th=1