Kit avalable from Jaycar KC5499 @ $199 mutch cheaper than an equv comercial unit here. Its powered from 12V dc @2.5A. The transducer is driven with 250V AC squarewave. The PIC micro comes pre programed that drives it.
What about ultrasonic humidifer elements, couldn't they be used for ultrasonic cleaning if the tub was redesigned, and frequency lowered a harmonic or two?