Two methods spring to mind.
The first is to define a cylindrical coordinate system, and then constrain the shaft surfaces with reference to this. You can then constrain in R (and optionally Z, i.e. axial movement) but leave the Theta (tangential) direction free. Note that this gives a completely rigid constraint in the other directions, so the shafts will not be able to tilt or deform out-of-round.
The second, and typically more accurate, is to create two points very close together at the centre of the 'bearing'. Link the shaft surface to one point using a Weighted Link, connect the two points together using a (very stiff) Advanced Spring, and then constrain the second point, leaving one rotation free (and optionally one translation).
A third way would be to use a frictionless contact constraint to a fixed outer sleeve...