Those phone protectors covers?, they diminish the display by a considerable amount in favor of protecting it. Well mine does.
In seriousness, I doubt that would work for VR where your eyeball is a centimeter from the lens. You would probably see the protector (or dust under it) which if it is anything like my iPhone screen protector would be like looking through a screen door before you see the other screen door
if that worked then you would be able to get them for spectacles, DSLR Camera lenses, VR lenses etc, also they would have to be model specific as the lenses have different curvatures to each other.
BUT! not all is lost. As @Heliosurge said, get the spectacle snap-in addon and order clear glass prescription lenses for them. That way you have a protective layer which you can scratch as much as you want then replace it. A good idea for business users actually.
The biggest issue I have with my Rift is that condensation, sweat and eye lashes stick on the lenses (Beat Saber's fault!) so I microfiber them after each use. It looks like blurry scratches if you leave that to dry,