When you are talking about those "water-proof pouches", do you mean those hard plastic containers that hang around your neck? They are about the size of a soap dish container. They have a hinged top part which latches down onto the bottom, and is sealed with a gasket that goes between the two parts. Is that what you were reffering to? If so, I did see them for sale onboard my cruise ship. I also saw them for sale in camera shops stuffed with items to clean camera lenses. .
Also, I thought of another important thing to bring:
- A light sweater, windbreaker, sweat-shirt or something similar to protect you from the chilly wind. At night, on the top deck, when the ship is travelling at full speed, it gets very windy. It will be very windy and chilly to those who are sensitive to cold temperatures.