If you haven't already, you may want to post this question on the Aus/NZ thread, that's where a lot of the locals go for questions such as these.
I can't think of any battery powered buttons like those myself, I have a mixture of Samsung Buttons which don't appear to be available in Aus anymore (?), Hue Dimmers and IKEA On/Off switches, which you will need an additional hub of some sort to pair with.
Simon
