Like stevenq99 mentioned, timing will be an issue for you if you're arriving on a cruise. You'll have to find a dive operator who leaves later, or is willing to have a late departure for you.
There have been a few recent threads by cruise divers. Just do a search for "cruise ship," "cruise" or scroll back a few pages and you'll find them.
I haven't used any of these dive operators personally, but cruisers on the board have had good luck arranging dive trips with Scuba with Alison, Scubatony, Papa Hogs and Blue Angel.
You should also head over to the roll call boards on cruisecritic.com and see if you can find other divers on your cruise who would be interested in doing a charter with you. If you can get 5 or 6 divers then you'd be able to get pretty much any small boat operator to do a 2-tank trip on your schedule, if they are not already booked.