Foxeer 2.5mm Lens - (115deg FOV, non-fish eye)
is on back order
Direct replacement of the standard 2.8mm lens of the HS1177 series cameras. This is not the run of the mill 2.5mm that has the crazy fish-eye effect that distorts everything.
It is as close to the 2.5mm lens on the GoPro as you can get - with very little distortion while drastically increasing your field of view. See the screenshot for yourself, and standard 2.8mm lens with some grass stains for scale.