Hi Anton, do you mean the one that goes...
Oh it's a grand old team to play for,
It's a grand old team to see
And if you know your history....etc
They usually crank out a crackly old recording of that at the start of games, usually immediately after "You'll never walk alone" which they enter the stadium to. Many club's fans sing a version of this but if you are planning to sing the Celtic version i'd advise you to be extremely careful of your audience. It could get your throat cut in Govan for instance.
I'm afraid my serces for the complete lyrics bombed out too. There are Celtic CD's on their main webpage, but they don't give track listings, i'd expect it to be on the anthems CD though.
All the best,