Try the Miami Convention and Visitors Bureau. If you can't find the info on the website, I'm sure a phone call to a knowledgable person there could give you a list of hotels that offer cruise packages.
Although this won't help you much now, the New Orleans Convention and Visitors Bureau website has a page devoted to hotels that offer packages: NOCVB
We stay in the Hilton family of hotels. If I were departing from Miami, I would call the 1-800 number and ask which hotels offer cruise packages. (Not affiliated with Hilton, just a long-time happy customer!).