Does anyone know where they sell Hawaiian sea salt in the OKC/Edmond area?

Might try Market C, Forward Foods or Native Roots. If none of those have it, they can get it for you. I know each of them has a nice variety of salts. If you're ever up in Tulsa, try Whole Foods.

How about Sage? I know they have a salt bar option on their menu.

Not 'local,' but Williams Sonoma has a decent selection of salts.