You could try creating ads about having found a paper wallet on social media and maybe some online communities that are popular in Victoria, Australia. I assume that many cities have online communities where you can find local news, events happening in your community, local sales threads, ads for local businesses, and things like that. I know several such places where I live and it's not uncommon for people to post they found a wallet, a pair of sunglasses, ID cards, credit cards, and many other physical items. If you are lucky, the person who lost it could be browsing the same sites.