"The part no."? There's lots of different styles. Just search eBay / Google for fender vents or fender portholes. You'll find tons of stuff. Putco makes some, and lots of others do too. Saw some Escalade style ones on a Denali a few months back -- they were installed upside down and looked silly. I have some, but in a style I can't find anywhere at the moment. Happy searching, and good luck!