Mannieg, I would not spend a fortune on used OEM ebay bulbs as you have no idea how long they will last. The retrofit kit from the dealer uses halogen bulbs, not HID's.
I would pull one of your headlight housings out and see it you could use a common size HID bulb & make your own adapter plate to secure it in place. I know that it can be done, it just depends if you wanna spend $500 bux for one someone else made or if you wanna spend $90 bux on new aftermarket HID's with ballast & then fab up your own adapter plates.
If you can handle this yourself then I would find your own cheaper solution, If it seems a bit to complicated then maybe I can help you & we could figure something out. I have always been good at fabbing things up & getting them to work while still looking good.
Your factory HID's are 4300K, If you want a tiny bit more purplish color you could go with a 6000K or 8000K for a blue color. 4300K will produce the most usable light though. I have 6000K HID's in my car if you would like to compare them sometime.
Good luck, Rich