buy some sharingan contact lenses :D but i think they cost quite a bit
I suggest both the head band and the kunai. Any other item or paraphernalia would be "corny" or geeky. Besides, those two are the most popular symbols of the Naruto anime.
Kunai... you can't really use it.
Head band... really awesome. :)
naruto headband sounds cool! and u could actually wear it whereas if u but the kunai u cant actually use it much unless your doing cosplay :)
buy a whole kakashi outfit