I am jealous, we can't get the fuel efficient small car that you guys have in the Europe. The air dam is made of unobtainium. Really expensive stuff. Almost obtainable....
Actually, my target for all my modifications is to make it recoverable from the savings made on gas mileage improvement and to look pro. I used a piece of landscaping edging. It took a while to find one that would fit and not look stupid. I had to form the plastic to fit. I'm not entirely happy with it, but it is solidly on there and it doesn't look stupid.