They were originally available from universaltire.com but they no longer have them. Then simpletire.com had them but are out of stock. That is why I suggested the Zeetex as an alternative since it is about the same size. I cannot vouch for it though because I'm still running my Austone and know nothing about the wear or handling of the Zeetex.
Universal has a Dunlop very similar to the Austone and they claim to have 2 in stock. https://www.universaltire.com/175r16...axi-black.html
Expensive as hell though.