There are no harp stores on the Islands of O'ahu, Hawai'i, Moloka'i or Maui, and to my knowledge, no music stores on O'ahu carry any harps, even the popular, 26-string, four pound Harpsicles built by the Rees Family in Indiana. The Harpsicle is an excellent entry instrument with a superb sound for the money.
Sylvia Woods, a world-renowned harp player living on Kaua'i, has a limited stock of harps available at her studio there. For many years, Sylvia had a harp store in the greater Los Angeles area, but now runs her business online. Contact her for more information. Sylvia also has a wealth of sheet music available as immediately downloadable PDFs.
I would never recommend purchasing a harp before playing it! EVER! I did that once, and learned my lesson - it was a fine harp, and I sold it later to someone who was happy to receive it, but I did not care for the sound. What sounds good to me, may not sound good to you. The first rule of thumb is that you must resonate with the harp. If you don't, you won't play it.
How do you know a harp resonates with you? Because you won't be able to pry your fingers from the strings. Your body will tell you. The musician deep within will tell you. Trust me - you will know! Ask any other harp player.
The US Mainland is the place to go to check out a wide selection of harps. Three recommended stores: