I would agree with suggestion to contact Jetpets here in Australia.
I have never used Jetpets, but they are used by dog rescue services here and are well regarded.
Good luck. Senior dogs are generally such beautiful souls.
One really long shot maybe a cargo airline crew taking your dog in cabin with them. I would be surprised if this were practical but maybe.
Or possibly instead of your planned cruise, you take a passenger carrying cargo ship with your dog?