The Sandpaper TP is one of the few things that can be sucked out of a vacuum style ship toilet. And at home, I use a spray bidet and swear by it not at it. So, when I cruise it's a bit of a change. My suggestions?
1. Not as good as regular bidets but, can cut down on TP. A travel bidet. Best is to look on Amazon and check out rankings of travel bidets on the web.
2. You can even pick it up at a dollar store. Go for hydrocortisone goo or hemorrhoid cream.
That way you can cruise with confidence without worrying about down there discomfort.