Anyone Who Read The 'neon Green Helm' Cheat That Couldn't Find It:

A more accurate way to find the 'neon green helm' or 'Fin Gleam'.
Look at anvil on your map, and fast travel to the lighthouse, if you look back on the map, there should be a little island west of anvil, head over there. Once you're there, go into the water to the west of that island, and head underwater. The Helmet should be in between 2 large rocks, laying in a pile of bones.