if you can get hold of the co2 bottle inflation jacket that would be a good starting point, a signal mirror, sea dye, an epirb, a whistle, all tethered to the vest if possible.
I knew some guys who carried small radios, sealed in a bag i think, then again i also flew with a guy who had some diving goggles and a mini breathing bottle, about the size of a coke can. It always made me smile to look over and see the divers googles swinging from the door.
plan to wear everything on your person somewhere, it is no use floating around inside the cabin, should you ditch it will be gone.