A search for breton at  J C's Tunefinder   will get you a lot of references (though it will of course include "Cape Breton" too) -plenty to be going on with, anyway: available as staff, midi and abc.  Of course, it's best to listen to the music before trying to play it; "sheet music" can only ever be an aide-memoire, and will give you no real idea of the kind of style you need.

Malcolm