I have a travelon anti theft fanny pack and it works great. The buckle is right next to the pack and it has clips for the zippers so it needs to be unhooked before you can open it.

Travelon Anti-Theft Active Waist Pack, Black, 9.5 x 6 x 2 https://smile.amazon.com/dp/B01E5JKUUG/ref=cm_sw_r_apan_i_QJ1207M8W7XJFSW9RSTJ

https://www.amazon.com/dp/B01E5JKUUG/ref=cm_sw_r_cp_api_glt_fabc_CJH0MF4N82F5QW62YPVY

This is the best fanny pack I’ve found in regards to peace of mind. It’s also made of very high quality materials i.e. slash proof straps. You can lock the zippers and the belt buckle on the pack itself to prevent theft, and there’s a zipper pocket that’s flush with your body perfectly sized for your phone. I seriously can’t recommend it enough!