Are they not just rota grids? Pretty sure the sydney dealer should be listed on rota website? For WA, most 18" rota sets (especially the older designs) are only 1k for a set of 4.
Only sucky thing would be you'd have to buy a pair cause dont think they do singles....but at least that way you would have a set of 5 and one spare cracked wheel lol and only be in it for $550 plus whatever tyres you have...
Rota Dealer:
NEW SOUTH WALES
Play Racing and Development
Unit 10, 21-23 Bay Road
Taren Point NSW 2229
Tel: (02) 9540 9500 Email: jt.mechanical@hotmail.com