Volunteered myself at a new high school's drama department. Have made a maid's bonnet and two british sailor hats and am working on their big Commander's hat. Don't know if the Aussies use this hat in their Navy, but here is a Yank's version.
Materials; Poster board, florist wire, wide bias tape , black broadcloth, white broadcloth and my new sewing/embroidery machine. I have to make 9 of these, have made 2 already. Have already cut out all of my pieces and only takes me 3-4 hours each if my sewing machine and everything else goes as planned.