There lots of song books published by modern day collectors, usually on their own County. Jimmy McBride from Inishowen and Jim MacFarland from Derry have a book out on local songs. Jackie Boyce from County Down has a book out on songs from County Down. John Moulden has pampklets and books published also.(search 'Ulster Songs')
You just have to search for them, they are still available.
       Songster