Dave at the surf shop in Pambula (5 min south of Merimbula) might be able to help.
Or.. try Simon at the surf shop in Merimbula (next to the ice cream shop) might also know.
Ask Simon if you can hire his 11'6" Naish..

.. Let us now how you go.
Also.. there's heaps of SUP'ing at Merimbula pics here if you've not seen them.
www.seabreeze.com.au/forums/topic.asp?TOPIC_ID=44361&SearchTerms=pics,from,my,mambo,tripDJ