Try this site. I think it will do what you want.
It is a bit of a PITA to travel thru but it will do. Go to site of Southwest airlines -
Click on Special Offers at the top
To the left of the screen click on Cruise Specials
Scroll to the bottom of the page to where it says "More Cruise Specials:
Check out All of Our Top Deals >>" and click on that.
Pick one of the lines that is offered in the section of Last Minute Cruises. (Trust me on this one. It looks like you will not get any other sailing but thru the end of the year but when you look thru and hit the "Continue / More Info" button on the dates for the cruise you get the rest of the next year dates)
No go thru to fill out the rest of the info after your dropdown dates - # in party, location, past guest, etc.
Chose the type of room you want
AND WOOOHOOOO - YOU have gotten to the page of all the available cabins on that specific deck.
Like I said it is a bit of a PITA but I do like this one to see where and how many available.
If you need more info or if I was totally confusing PM me.