Here is a link for Novelli Brisbane and phone number along with other Novelli contacts.
https://www.bing.com/search?form=MOZ...velli+brisbane
Best give them a call and try to identify the correct assembly.
Or maybe an email with a pic of the complete assembly.
I doubt you will buy the piece only but you never know.
Being duel flush they have a tendency to slam the valve shut which in turn causes damage.
I have replaced a few for friends over the past few years, some Reece over $100 for the assembly, and a couple from Tradelink about $25 to $50 depending who serves you.