A couple of ideas...

* Using an H-bridge to drive both sides of the transducer will double your effective swing available from your supply.

* A square wave oscillator that’s filtered with an L-C low-pass will give you roughly the waveform you need.

Such a thing could be constructed from CMOS buffer logic, including the oscillator. With both-sides drive it would happily work on 5V, which means you could power it from USB. Something like the CD4050 for example: http://www.ti.com/lit/ds/schs046j/schs046j.pdf