I assume you've had a chat with the marina people. We got a very good rate (after - shudder - Sydney
prices) in Mooloolaba so it could be worth going over the fine print.
If their prices are out of reach what about the pontoons in the Newport
canals? We discussed using one in Mooloolaba and attractive prices were mentioned but the Marina were very accommodating.
shows a few boats in the Caboolture River, but it could be a bit shallow.
Local brokers, chandlers or slipway workers may be able to help, otherwise it's ear to the grindstone.