We have ASIC (Australian Securities & Investments Commission) that handles company registrations, notices, etc. and they maintain a register of insolvency notices and liquidations.

This can be a reasonable place to go to look for distressed businesses/assets too and I've considered using them as a source with my aggregation/search engine, though they don't really have the same type of information as a business for sale listing so they fall somewhat outside of the main type of results that I otherwise display.

Other reasonable places I've seen too, though in incredibly low volumes (think 0-3 listings a month), are commercial auction houses/sites where they'll list a business for sale or the full assets of a business. The main issue with that it is that they're so low volume that I'm not sure it's worth spending the time ingesting them this early on while there's still many other larger listing sources.