I need a classical piece to set libretto to...?

My friend would like to write something for me to sing, but neither of us are adept to coining a melody. I'm a soprano, and sing in a classical style. I'd like help finding a piece to write lyrics to... something with a strong melody, which could be sung in a range from F below middle C to high E. Something that isn't extremely widely known would be preferable. Thanks for your help!