Have a search of the forum for 'GoPro' and you'll find a few posts on ideas, you can either buy someone's custom 3D printed goggle mount, or make/modify your own
Pick your preferred mount fitting, get some PolyMorph and form a blob of it to fit between the fitting and your goggle. If it goes wrong or you want to refine it then reheat the PolyMorph in hot water and change it
Not exactly the same as this but it should give you an idea
You can get PolyMorph at Maplins or online.