Add built in webcam to laptop?

I just bought a Compaq Presario CQ56 from a pawnshop. I saw that it had a shaded plastic rectangle area at the top that I was confident was a webcam. I asked, and the guy that sold it to me thought it was too. But i came home and found that this model, xg635ua#ABA, does not have it built in. But other models of this laptop do. So could I send it in to the factory and have one built in. The area is where the webcam would go. But it has a shaded plastic area. And if i could get one installed, how much would i be looking at? The laptop is great just missing that one feature.