I've not personally heard of a successful product for that. You could try a headlight restoration kit, but you'd likely end up with a lot of crazing and micro swirls that would distort your vision once the sunlight hits them. Can't hurt to try though, since the visor is basically a write off at this point.
If someone has heard of a scratch fix, I'm all ears!
But after the expense of purchasing the polish and the elbow grease, you're probably better off just buying a new visor for something like $15. Especially since you'll probably create some warped spots in your shield that will affect your vision depending on how deep the scratches are.