I've seen several Elky's in the Pittsburgh area sporting visors back in the late '80's to mid '90's. Those were the "old man" rides back then with other trim on them like the ol' curb feelers & static straps.You're talking old school accessories. I've never seen one for a G-body before, only on earlier '40's, '50.s, maybe '60's cars.
You could ask some low rider guys, or get creative and make your own.