HOSCO makes good files (MIJ) and there are suppliers in AUS. They sell them individually (S,M,L) or sets of three LIKE THIS.
That is just one suggestion and one retailer. No affiliation, but have bought other parts from them. Good to deal with IME.

Mine are from Stew-Mac but I suspect they are made by HOSCO. The exception is the SM ones have two sizes per file (different one on each edge). When I need to replace them I will probably buy some HOSCO's.