Um, from a Boxster, maybe?
You might look at the side intake from an MR2 to see if it will fit better. There are some photos floating around here of someone's effort to put a NACA duct in the side valance.
You'll need to do some of the fabrication behind the grille yourself. The NACA duct example I'm thinking of used a soup can bonded in with fiberglass as the hose connection.
Unless you're going for a particular look, it might be better to duct air from beneath the car into the upper engine bay to get cool air for the intake. Less bodywork involved, and it will look stock from the outside.