There is a dwarven weaponsmith in the Dwarven District of Stormwind who can craft with lightforge iron. His name is Grimand Elmore.
I've packed the iron you found into a crate. Take it to Grimand and tell him your tale. I'm sure he'll oblige someone on a quest such as yours, and craft for you a weapon - a weapon to give even Morbent Fel worry!
