Some people use Carefree Side Visors, this eBay listing
has really good prices on the standard ones that use a suction cup to hole them down, better ones (even power) are available but much more expensive. Call them at 800-328-5100, they may have some of the other types at good prices also.
I purchased 3 of the 30" Power Smart Visors from ShadePro for our windshield, they arrived in great condition and am installing them soon, hopefully within a week.
is considered by many to be the best manufacturer of this type of shade, they are pricey but reliable and stand behind their work. They attend most of the big rallies or if you are traveling close to McKinney TX they will do your measuring and install there.