You could make similar device using large PVC piping and fittings. It looks to be about 6" in diameter. Piping or duct could be used depending how durable you want. Just glue a socket cap on the end of a pipe, cut to your specs and glue a socket to thread adapter on the other end, wrap some teflon tape around a threaded plug, screw it in and viola! You have a waterproof storage tube. You can line it with felt, foam, or anything else you want to protect the contents.