2. I used a broad brimmed straw hat that was never comfortable on my head. I cut a 3.5" wide visor from the brim using the helmet as a guide so it fit snugly up under the tiny plastic bill and tapered around to the sides behind the ears where there is a vent hole. I cut a generous width so it would shade the sides of my face too. Sort of a cross between a bonnet and baseball cap shape.
Once I was satisfied with the shape, I punched 4 metal eyelet holes (fabric shops have these) lined up with vents in the helmet. Then I sewed a cloth edging around all the edges to keep the straw from fraying.
I tried to find some sort of plastic but failed to find anything suitable. Stiff enuf to hold its shape in the wind but flexible enuf to form the visor.
It was a big hit with the other bikers. They said I shud market it.
I attached the visor with skinny 8" cable ties threaded thru the eyelet under the plastic bill and thru the vent, snugged tight and made sure the head was in the vent hole so it couldn't scratch me. Clip the ends off and black ties makes it invisible.