Fotodiox GoTough Silicone Mount with Neutral Density 1.5 (ND32, 5-Stop – Fotodiox, Inc. USA
Amazon.com : TELESIN 3 Pack Neutral Density Filter ND8 ND16 ND32 Compatible with GoPro Hero 9 Black- Lens Filter Kit Lens Protector for Go Pro 9 Camera Accessories : Electronics
Glass ND filter for GoPro Session 4/5 – Camera Butter
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
TELESIN ND4/8/16+CPL Lens Filter Protector Filter for Gopro Hero 5 6 & 7 Black | eBay