I had the good fortune to buy Headshot's RS6. In the fall I had the front bumper fully clear bra'd and in doing so had to remove the front lower spoilers to get them done separately.
While I have them off the car I took some pictures of them and a friend of mine sent them to a body shop he know to get cost to reproduce.
All said and done, it appears I can get set's made for around $300. I'd need to get a minimum order made as there is a significant one time cost to get moulds made. They would be fibreglass and I suspect the would come unpainted. They'd closely match the ones for my car so any body difference in your cars would have to be figured out personally.
Here is Headshot's original post...
Here are two pics of one of the spoilers
I'll see interest before going any farther.