[Perfectlap]

Go with Ebay. Some of the better known dealerships sell on there.
You can get the sideskirting (factory) for about $700 and the factory front bumper upgrade (GT3) for $900-$1000. Add some 18" 5 spoke Carrera lights $2K and you've got a pretty nice look.
Some people go non-factory on the aero with fiberglass parts but those require more work to fit properly and like all fiberglass vs. Poly-U can break easier and that's NO FUN.
I added GT3 Recaro Pole Position racing seats $2K-$3K that matched my red interior perfectly.
My old car was a 1.8 Miata with a full Racing Beat aerokit and BBS RK's and lots of suspensions mods (for racing not looks).