CP is right, there are a ton of ways to do it.
The issues you need to think about are time, cost and result. As in: How much are you willing to spend? How much time do you have to put into it? What end result do you want?
If you have unlimited funds you could commission one. If you have a bunch of cash and time you could go the dual-layer motorcycle visor route (there is a whole thread on that). If you have a limited budget but time you could use some form of pliable plastic and do your own work-around.
It really depends on what is specific to your needs and means. There is a ton of information here on making visors that should help you once you narrow your parameters a bit.
"I don't know what's weirder, that you're fighting a stuffed animal, or that you seem to be losing" - Suzie