Combo ticket for Oriental Pearl Tower and Huangpu River Cruise

I am struggling to find the combo ticket of Pearl Tower and Huangpu River Cruise. We want to visit the Pearl tower and then do the evening cruise (the 45 min to one hour cruise). We went to the Pearl tower and the booking counters there said that they do not have the combo tickets even though it is widely displayed on the boards outside. I was not very clear if they do not have such a combo or if they were sold out for the day. We went there at around 5 pm on a Saturday. I also called (021)58791888 and they said that indeed there is a combo ticket but they did not know where to book it from. Can some one pls help me know where can I buy the 200 RMB Combo Ticket (upper sphere, Shanghai Municipal History Museum and Huangpu River Cruise)? Also, till what time does the cruise operate as we want to do an evening cruise.