The Australian Nintendo eShop doesn't have a browser based storefront, but it does have purchase pages for the games if you know the NSUID code. For iOS users, I've made a Shortcut that you can run on a UK game page and it will open that game page in the AU store so you can purchase it.
I use Deku Deals to manage my Wishlist and as an Australian user it defaults to UK eshop links, which is why I focussed on making this Shortcut work with those.
To use it, open the UK store page for the game you wish to purchase in Safari then run the Shortcut from the share sheet. It will open a new Safari window with the AU game page, which you can buy from.
https://www.icloud.com/shortcuts/d8c3dbd7bb514d04bab83af156c…