I'm thinking about it, as my boat is very small and a dinghy of any kind is impractical.
I was looking at porta boat (too expensive) and kayak, but kayak would be as long (nearly as long) as my boat, so also impractical.
I also figure that if it can be easily pulled ashore, it can be folded up and chained to something substantial to prevent theft.
Materials are available anywhere in Oz. PVC fabric is harder to find, but is available. Trimmers and awning makers use it. Most shade sails that are waterproof (ie not just for shade) are PVC fabric of some kind.

I like that Wooden Widget link are you intending to make one? my only problem is 30 pounds and you dont know if you can buy the materials required to build it in AU its a lot of money not to be able to build, but it would be sooo kool to build also