after starting into my own ventures in carbon fiber, i would be extremely careful buying carbon fiber parts from a non-reputable seller... if its branded youll have a tough time telling if its authentic. and if its not, its very time consuming to make sure its adequately protected (from UV, heat) and will last a while... the materials are considerably more expensive as well.
if you do go with an ebay one, do yourself a favor, and pick up UV protectant online somewhere, apply it yourself, and bring it to a body shop to get 1-2 coats of clear. not so cheap anymore but at least you know what youre getting. from what ive heard even some of the more expensive CF dealers dont go through all that hassle, and weve all seen yellowed CF hoods for sale.
