GoPro Hero 4 Session - Polariser / Red Filter by PolarPro - REVIEW - YouTube
Amazon.com : SOONSUN 4-Pack Lens Filter CPL ND8 ND16 ND32 Filter for GoPro Hero 5 6 7 Black, Neutral Density and Circular Polarizing Lens Filter Kit Lens Protector for GoPro Hero 5 6 7 Black Camera : Electronics
PolarPro Polarizer Filter for GoPro Hero 7 / 6 / 5 Black
Amazon.com : CPL Polarizer Filter for GoPro Hero 11/10 / 9.with The Filter Adapter, You can Also use All 52mm Camera Lens Filters on Gopro 11/10/9 : Electronics