Do you know the L/D ratio at whatever angle-of-attack is being used in the turn? If so, in a steady-state constant-altitude turn, Drag = (D/L) * Weight * Load Factor.
Note that the ratio of Lift / Drag is also the ratio of Lift coefficient / Drag coefficient.
Note also that the L/D ratio can easily be computed, if the Thrust or Drag for the same angle-of-attack is known for straight-and-level flight.
In a turn, the airspeed must be increased according to the square root of the increase in wing loading, to allow steady-state flight at the same angle-of-attack as we had in wings-level flight.
This answer treats the drag due to increased loading due to turning as being exactly equivalent to the drag due to increased loading that we would get simply by adding weight to the aircraft. This is not exactly true, because in curving flight, the relative wind is actually curved, which has aerodynamic consequences. But it is a very good first approximation for aircraft that have reasonably high flight speeds, and it is really the only practical way to tackle the problem short of an elaborate computer model.