Try looking on Wizard101Central for a list of the grand storm items.
I know for sure that Gurtok Firebender drops a grand ring that gives an increase in power pips, and the Gurtok Piercer drops a dagger that is basicly the same as the ring. If your going for power, then try getting the ring from Orrick NightGlider in the Gauntlet of Woe, as it gives health, power pips, and an extra 5 damage to your storm attacks.
Hope I helped.
Seth ShadowCloud Grandmaster Fire/Storm Former pvp Veteran A good friend
Seth EmeraldFlame Initiate Myth Former pvp Knight A good friend