This is a hybrid found in Melbourne which seems to be a cross of leucantha and ? Leucantha is a very popular plant and ‘Annie B’ is also though not well known. In autumn leucanthas tend to sell out so you could look at ‘Annie B’ instead.
Queensland has what looks to be a similar cross in photos called ‘Rosh Eden’.
An evergreen plant to about a metre, it has purple flowers probably mainly in autumn but then seems to hang on throughout the year. Seems reasonably frost hardy, for sun.