Any leads can be nulled and used for continuity measurements. Any lead resistance is negligible when insulation testing, so that would also be OK with any leads.
However, unless your tester allows you null the loop/RCD test leads, the calibration of the meter is dependant on the loop/RCD test leads it was calibrated with. Second best fix in the short term, is a replacement set from the original equipment manufacturer whose production tolerances should ensure minimal deviation from the previous set. In the longer term, recalibration with the new leads is the only certain way of ensuring the performance the manufacturer intended.
If the tester was a Fluke 15** series, which as far as I am aware, are the only meters which require the loop/RCD test leads to be nulled, then you would be able to use any leads in that case.