I just placed an order for the parts necessary to install aftermarket OEM-style 2012 3rd gen Prius 5 integrated fog lights onto my 2012 Prius 4 base model. I had to order the lower radiator grille from a Prius 5 and a pair of OEM Toyota Prius (2010-2011 model) for complete lights, wiring harness and switch. Since the 2012 model Prius has an integrated light stalk with the fog light switch on it (and fog light indicator on the electronic display), wiring it so it’s 100% OEM-like will be too costly and time consuming. At the same time, I also ordered the rear center armrest console tray that Toyota decided to omit from the 2012 model.
As soon as I receive the parts, I’ll post up a do-it-yourself installation guide not too different than the Acura RSX guides available on this site.
EDIT: I should also mention that I’ve also ordered a set of high power LED projector fog lamps for the Prius, NOK9560.