The only places I knew of that had Platypus in Oz some years back(10 years or so) were Healesville and Melbourne. Things may have changed since? I first saw one in Melbourne's exhibit many years ago. Later found they were almost easier to see in the wild!
there's a few more than two now but you could probably still count them on your fingers and have some to spare. A long way from "every zoo or native fauna park you visit has at least 1 platypus"! Off the top of my head: Melbourne Zoo, Healesville, David Fleay's, Lone Pine Koala Sanctuary, Warrawong, Sydney Aquarium(?), Taronga Zoo, Platypus House in Tasmania ..... I can't think of any more but I'm sure there's an Australian member (say, Hix) who could give a full list
Ahh cool, thanks for that (also, it's not off-topic. We were going off-topic by talking about platypus )