I'd recommend Cruiseplus. Their website is www.travelandcruisedeals.com
and phone contact is 1-800 854 9664. We booked a cruse with them this fall and were quite pleased with the price.
I also recommend you spend the extra and get a balcony, especially on the Alaska cruise. We went 8 years ago and had to take an inside cabin because we booked last minute. Never again, there is so much to see and I feel we missed a lot.
Cheers