Hi Dom, the first place to look would be the "Buy and Sell" section on seabreeze. It's sorted by state and board type, so you might find what you are looking for. Also a good place to sell it when you leave.
Good luck.

Hey Dom, there are several shops around the coast that sell secondhand SUPS. At Noosa try Adventure sports in Noosaville. In Maroochydore try Ocean Addicts or as said earlier try Seebreeze. A lot of the boards are on the coast.
If you like hype and crowds give the Noosa Festival a try. If you are more melow good SUP surf can be found all the way from Coolum to Noosa and from Yaroomba to the Maroochy river mouth.
Enjoy the coast.
ET

thanks guys - couldnt find anything suitable to buy but rick at noosa standuppaddle
gave me a good deal on renting including trying different boards and some lessons
for my girlfriend - reccomended

loving noosa - as a goofy i am forced to practice my rights !