G'day folks,
Your chances are better in WA than over East, at any rate. Gumtree seems to be the best option over there.
But keep in mind that these are a professional grade piece of turf equipment.
So the old saying usually holds true; good ones ain't cheap, and cheap ones ain't good.
Of the brands you may encounter, Alroh and MEY are out of production, and parts will be difficult. Mowmaster/Dwyer & Felton and Ings are still made [in WA, too], though.