Where can I get sheet music for a Hymn?

Me and my Fiancee have chosen 2 hymns for our wedding and the vicar has told us today that the organist doesn't know one of the hymns =S the hymn is "We Pledge Our Selves To One Another" Where can I find the sheet music for the organist? We cant chose a different hymn because we have already printed the Orders of Service. Any help would be great!!!!