When a previous employer went bust, it was bought by the CEO after being listed by the administrator on an obscure website (ip-bid.com) which you have to make an account and log in to just to see the listings. There was only one bid. (I leave to the reader to speculate on the utility of a bid website without public listings, but such listings might represent good value compared to those advertised more widely). It may be worth checking company filings to see if there are equivalents used by insolvency administrators in Australia (I found out only by reading the administrator's "statement of proposals" on the fillings website after the fact -the sale wasn't advertised anywhere else as far as I can tell).

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.