Most shops that sell aftermarket parts can usually get you stuff like this if you need it. If you're lucky enough to speak Korean I'm sure you can order from that site directly and get them to ship it to you.
Nope. Not really stupid at all. I did before with one of my cars. I knew 100% I was going to get the car so I bought upgrades for the car even before I officially purchased it. Once I bought the car I put everything on it right away. As long as you're sure that you are getting the car theres no reason why not to buy the parts early.
Tons of Optima performance parts upgrade - a cool way to make some gas burning rubber to a car.
______________________________________ car parts/accessories/performance upgrade
EBAY! LOL. All joking aside I've bought a lot of car parts from ebay. As long as you make sure that the listing is legit you can usually find good deals on Ebay.
I bought all of my esterior parts from this site and although this is a Korean Company found it to be a fast shipper (they send everything certified though so you have to sign for it or leave notice to allow carrier to drop off parts at address or neighbor).
Also don't change your mind and want to return anything as USA to Korea shipping will exceed the cost of the item in most cases (seller does not pay for return shippig costs).