I was told by a friend, who complains of not having thick hair, about an Aveda product that seems to "increase" the volume of the hair and make it appear less thin. It's apparently a powder that suits any colour hair. I was told that one can find all the details, as well as comments, on the internet. The full name of the product is:
Aveda Pure Abundance Hair Potion.
Sorry, but can't talk from experience but just by looking at the friend's hair I see a big improvement.