How to use CR2032 button cells for excitation of load cell
CR2032 cells have quite high internal resistance. Any decrease in voltage due to the load will only be worse with stack of CR2032 cells. 

You need a voltage regulator, not a better kind of battery. For example, if the end-of-life voltage of your 9V cell is ~6V you could use two in series and a regulator to give you 12V.