That's the lip from the OEM Ground Effects package. If you don't have the front/rear lip and other side skirt, it's going to look a little out of place.
If you want a good finish, have a shop paint it. Get several quotes before you do so.
Technically it's possible that you can get the same finish with a rattle-can. But you'd have to be very good at it. And even then the paint probably wouldn't match.
Try junkyards.