You can't buy that spoiler anywhere.
It is a one-off that I made in 1,5 mm aluminum. It was made as a repica of the early Gr4 1972-73 gr4 racers from studying period correct pictures.
It's actually a 3-piece design that's riveted together in the center - the thinking being, that while racing the car, damaged pieces of the spoiler can easily be replaced.
I actually made another for a bloke in Germany, but even then, I can't guarantee that it will fit other cars than mine, as the placement of the flares may vary from car to car.
It's also designed to work with/wrap around the oilcooler, so running the spoiler w/o the cooler will look odd.
Kristian