go to every mages guild in every city. some one usually has one for sale. and if you go to everyone one (except bruma ofcourse) and they don't have one, you'll have to go questing in ruins! on rare occasions, you'll find an empty grand soul gem in a chest, or cask.
oh, and when refering to oneself, always say "newb". "noob" is an insult gamers give eachother when they suck, "newb" is what gamers say to an inexpieranced player, who has the guts enough to admit they need help. you are a "newb"... as am I...