You can buy trout fingerlings from several places around Canberra. There are two hatcheries in Tumut, (Triton Trout and Snowy Mountains Trout) and a NSW government funded one down in Jindabyne (Gaden Trout Hatchery). Once a year the Canberra aquaponics community does a group buy of trout fingerlings around March and we meet at someones house to pick up our fish. Subscribe to the newsletter if you want to be notified of the details.
If you want to buy native fish, there is a hatchery in Wagga Wagga (Murray Cod Hatcheries) or you can buy them over the internet with a good success rate (for example I've had good success with aquablueseafoods). Once again, we run group buys every now and then for things like Eel Tailed Catfish and Silver Perch, subscribe to the newsletter if you want in.