Is the hot chocolate river cruise available?

I’m taking a trip to Chicago next weekend and have really been looking forward to doing the hot chocolate cruise they offer later in the evening.

I checked a few weeks ago and all they had was dates for a week out (two weeks earlier than the trip). And now it’s saying no dates available when I try and get tickets. Does that mean it’s sold out? Is it possible to get tickets in person once I get there or would they already be completely booked?