I think, from what Macfhionn said, that we can conclude that it's definitely Scottish and that the "na" should definitely be separate from the word following it (that bit is probably a mistake). Beyond that, I'm not sure how to help you. I definitely wouldn't advise using any of the pay services, as they are only in business to make money, and will sell you just about any heraldic device they think you'll buy (my husband was amused, once to have been offered a coat of arms for our surname..."Nickel." Since the Nickels are, and have been for centuries, German peasants and pacifists (the name is Mennonite), the likelihood of them ever having had a coat of arms is highly unlikely!
I know it's a slog, but the next step is probably more geneological research. For one thing, you're going to have to ascertain if you're descended in direct line (first-born son to first-born son) from the original person who was awarded those arms to ascertain if they actually belong to your branch of the family (contrary to popular belief, arms were awarded to individuals, not to families, and were only passed on from father to first-born son), and in the course of that, you may discover more about the coat of arms itself.