What most people I've seen do is purchase a light blue blazer from an op-shop cheaply.
The patches can be bought off ebay (search "ouran patch") or you could be cheap and print it out in colour and stickytape it onto the jacket.
You can sew purple ribbon onto a solid black tie. Or you could use fabric paint. Some people on the forums have used some form of iron-on adhesive.
Add black pants/shoes and a white shirt and you're done
(wig maybe, bunny, bear, glasses + folder, twin, depending on which character)
EDIT: check out the thread here http://forums.cosplay.com/showthread.php?t=80779
or do a photo search