Bob - what Royal said. You should be able to make your own for less than a couple of dollars. I found my needs were somewhat different than the stock units allowed...I cut the visor closer on the "button side" for additional clearance and extended the section over the screen for increased coverage. Hope that helps!
Bob - not to say the commercial ones aren't good ones too, but I was not quite happy with the shape of the ones available about 1 1/2 years ago so I made my own for less than $2.00 of materials and 10 minutes of effort. Works great! (Excuse the dust)