Is there a transit visa for Sri Lanka from Australia?

Yes. Australian citizens need a transit visa when having a transit flight in Sri Lanka.

Applying for a transit visa is easy even when you are in Australia or anywhere in the world, just a device with an internet connection (smartphone, tablet, laptop, ..)

Owning a transit visa will help you get to Sri Lanka easily and stay up to 2 days (48 hours). However, you can only stay at the port of entry (airport, ..) while waiting for the connecting flight. This means that, if Australian citizens leave the airport, it is a violation of the rules of entry with a transit visa.