I've thought about trying one
I've thought about trying one of the long brims, either one that fastens to your helmet or some of the bike hats.
So far I haven't had to deal with this situation very much due to direction of travel, treeline shielding the sun, etc. so I've just been squinting or tucking my head down more and pulling the brim of my Walz cap as low as it will go.
Maria Parker was using one of the add-on brims on her helmet with her Vendetta. Perhaps she or Jim can chime in on likes and dislikes.
-Eric