You could try Murphy's Law - buy three and a full set of five will appear.
Also give Deon Cameron (Narrabri) and Honest John (Newie) a call.
Please remember that these wheels are all 40 years old. I have restored old rims, and generally I would say it's not worth the bother (up to 12 hours per wheel). Typically, they corrode on the inside edge of the rim and won't hold air. Get five good centres, have Morton & May stitch 15" conversion outers on them, with a sandblast and powdercoat. You get a beaut range of contemporary tyre choices then, no rust or damage on the rim and 4-stud wheels.
When you add up all the costs, you can see importing a period-correct set of Westerns is a pretty good option.