just look on ehobbyasia.com for the front sight. Sometimes refered to as an "A sight" or "triangle sight".
Or any other airsoft place in the states (airsoft atlanta has tons of stuff).
It'd be way easier to get age verified and then search the classified and/or post a want ad. There's usually lots of front sights kicking around.
have fun, best of luck with your rebuild (personally, I think you're wasting your time...but to each their own).