Bunnings sell pots designed for flowering annuals that pretty much fit that description. Called "Bloomers" or similar. Not too dear and they often have smallis terracotta pots on sale in summer that only cost a few dollars. I don"t know if they have an online/post service, but you can search their stock online. Just keep in mind not everything they sell is online.

I have found the garden place at the back of Parklea Markets to be for less expensive than Bunnings and Flowerpower. It is attached to the markets but it"s a standalone garden place open every day and I have bought quite a few terracotta pots from them. Happy with all my purchases.