Bsale - This site specialises in selling businesses and also provides links to Australian businesses for sale by owners & brokers.
https://bsale.com.au/
Business Interests - Business broker/agent that offers post office sales in South Australia.
https://www.businessinterests.com.au/
Business Sold - Specialist business brokers that assist you in selling or buying a business in Australia.
https://www.businesssold.com.au
Businesses2Sell - Offers business opportunities in Australia and provides advertising to owners wanting to sell a business.
https://www.business2sell.com.au/