Dear Branwen23,This is one of my favorite songs. You can find it performed by Maura O'Connell and De Dannan on the CD "Voices of Celtic Women - Holding Up Half The Sky" from Shanachie Records (#78011). You can also find the same song/performance on this compilation CD, from the Irish Records site.
This song is also known as "Nora" - so you might want to search the Net using that name. The lyrics are usually the same as "Maggie", just switch the names.
Good luck, Áine