There is one in the back garden of one of the houses in Roslyn Terrace, in the West End. There is also one just inside the main gate of Glasgow University, also in the west end. But these are in captivity; there must be others in the wild.
By the way, the red phone box was designed by the grandson of the guy who designed Glasgow University and the son of the guy who designed St Mary's Cathedral.
And even more by the way, the design of the red phone box is based on the monument that sits on top of the grave of the english architect John Soane. Not many people, as they say, know that.