Any idea what the impedance of the transducer is?
Do you know if the transducer can tolerate a DC offset?
Do you have a link to the data sheet for the transducer?
If all you have is a 9V source, then all you can easily do is drive the transducer with a 0-9V squarewave, which obviously has a DC component. If the transducer cannot tolerate the DC offset, then you can Capacitively couple the transducer, in which case the transducer will get a -4.5V to +4.5V squarewave.
If you need more than 9Vp-p, then as I said earlier, you will have to use a transformer with step-up windings which will simultaneously boost the voltage and eliminate the DC component, or you will have to provide a higher voltage battery.