There is a young lady by the name of Siobhan Owen playing this piece on a lever harp and singing with it — video is posted on You Tube.
I love this song as well and looked around the internet for sheet music for it when I saw her video a month or so ago and never had any luck. LMK if you come up with anything!Helen
I suspect her spelling is off, and that may be why it’s difficult to locate it.
Typo…the Anglicized spelling is “Inishowen.”
You might also try searching on “Déanta”…one of their fan sites may be able to supply you with the music.