I don't believe there is any in Sydney and possibly NSW.
If you are looking for a club, I race out of Kurnell Catamaran Club and may pic up a Mozzie for myself to have a bit of fun (add spinnaker)
KCC once had a very healthy fleet of Mozzies and there are many pics of them up at our club. Currently we have members ranging from World Champs to novices in classes such as, Tornado, F18, A Class, Nacra 5.8, Taipan 4.9, Maricat 4.3, Maricat 5.0, Nacra 14 sq, Prindle 15. We also have a large catamaran division that races with us once a month.
Racing is on Sundays begining on the 2nd Sunday of September.