The go-to store for marine architecture so far as I'm concerned has to be Wickes, and while I was there to buy plywood I came upon sheets of pre-laminated XPS (extruded polystyrene) with a scrim of netting and cement. It addresses the need for something better insulated from heat and cold than plasterboard, so expect to see more of it.
I have though been on to the web authors to highlight it's ideal application to marine drones, or at least in my garage. And while I am not altogether happy with the text ~ I wanted its low radar signature emphasised ~ it passes muster.
Note too that it is produced in Egypt, and as a result is likely to be available globally. An alternative is pre-laminated PVC sheeting of the sort subbing for plywood in areas like signage.
I was offered a container-load whilst flying airliners in China, but then we all have regrets in life.
(Ed. the loser was also offered bitcoin at $1000 a pop).
