Lens Replacement for Gopro Hero 9/10/11/12/13 Black Cameras, Anti-Scratch Glass UV Lens Protective Cover Repair Parts Accessories Compatible for Gopro Hero 13/12/11/10/9 Black

Buy a replacement clear lens cover on Amazon - https://a.co/d/09miwSQn That should seal it up well and it'll likely not fog since the seal will be new. As others havs said, a little bit of clr or similar with a q-tip (don't touch the lens!!) and it'll be like new.