First and most important, call your agent and let them do all the work for you. It'll save you alot of time and hassle, and the rates will be exactly the same as the cruise line and they charge nothing for their services.
Second, you may have to open your search a bit since the one you want is sold out as there are some options available to you based on what I'm seeing.
47 Cruises & Counting! Favorites: Paul Gauguin to Tahiti: Uniworld River Cruises in Europe; any of the Celebrity Solstice-class ships; Holland America for 12-nights in the Baltics & Russia; RCCL for 14-night Greek Isles, Turkey, & Croatia; Holland America for 14-day Alaska cruisetour; 10-night Canada/New England cruise; 21 days in Hawaii including a 7-night NCL cruise; Oceania for 25 days in Asia; & 3 months touring Europe by train. And many days spent in all-inclusive resorts!