To my understanding, which is somewhat limited, It is unlikely that you will ever encounter an albino chameleon, though I am sure they occur in nature, they simply couldn't survive. An albino chameleon would have no protection (skin pigmentation) to protect them from harmful UV rays and would burn quickly under UVB lights. As you know, chameleons rely on UV rays to survive, so without the ability to bask under UVB, they would not survive very long.
I know that bearded dragons are the same way. There is no evidence that an albino bearded dragon has ever been raised to adulthood. There are White bearded dragons, though they have been bred to remove other coloration from their skin. These are called "Marketed Leucistic" Dragons. It is also possible to have a true Leucistic dragon, though I have never seen one or heard of a true Leucistic.
Yea, as far as anyone seems to know no one has ever produced or come across an albino chameleon. As close as you might get is the translucent veileds, but it's a totally different trait. But you do get chameleons with pure white patches and other patches of transparent skin.