Check the local forums here on NS. Sometimes you can find some cool gear there, the community is not that big and everyone is legit, you can good deals.
In Sydney the only Skishop that comes to my mind is Alpsport: www.alpsport.com.au
Other than that rhythm:https://www.rhythmsnowsports.com.au/ is a solid shop, i think. There are a few more jobs in Jindabyne f.e.: time2ride.com.au and not all of them have solid online-shops so you could always try and give them a call for the gear you might want.