The product is the Clamcleat CL257, though some places call it a C257. Search for either part number!
Ronstan are the Australian distributors for Clamcleat.
Whitworths (who have a branch in Cairns) list many Clamcleat and Ronstan products, but don't seem to list the CL257. I would expect they can order one in for you.
You can order one from ebay for about $40, which seems excessive, and they'd come from Europe.
Binks Marine in Adelaide want $28. Cost of shipping isn't obvious.
Adventure Safety in Melbourne want $31.16.
Deck Hardware in Sydney want $45.
Arnolds boat shop in Sydney want $26.17.
Boating Central, Geelong, $31.25.
Fishpond won't tell us where they are or how much they want, but they claim to have them.