I can think of two different kinds of mass produced piezo module that you might be able to find cheaply. The first kind is a piezoelectric speaker, an audio transducer, of the kind found in alarm clocks, alarms, and other noise makers. Here is an example of an artifact containing such a piezo speaker:http://www.dollartree.com/school-office-supplies/Tools-Batteries-Lightbulbs/Window-and-Door-Alarm-System/291c439c439p184790/index.pro The second kind is one of those piezo spark modules, of the kind found in some kinds of butane lighters. Here is an example of an artifact containing such a piezo spark module:http://www.dollartree.com/cleaning-storage-hardware/Household-Supplies/tools-tapes-adhesives/Click-n-Flame-Refillable-Long-Reach-Butane-Lighters/212c309c263p305704/index.pro BTW, both those links are from a retail chain in the Former US, called DollarTree(r), and the price of both those items is 1 USD, because that's sort of their gimmick. Everything item in a DollarTree(r) store costs 1 USD. Back to the subject of the modules themselves: the spark making module from the barbeque lighter, is good for making a brief pulse of electricity at very high voltage. BTW, I wrote an instructable on the subject of re-packaging one of these modules into the body of a ballpoint pen. This ible has some pictures of the modules themselves, and of some playful things to do with the finished piezo-pen, like (briefly) lighting old fluorescent lights, here:https://www.instructables.com/id/Piezo-Pen-Pulsed-Power-Source/ In contrast, if you want a continuous power signal, then using a piezo speaker, like the kind found in an alarm clock, or that door-window alarm thingy linked above. Of course to get a continuous electrical power out would require a source of continuous mechanical power, essentially sound power, input. Maybe you could drive it from a whistle powered by compressed air or steam. Or maybe some kind of thermoacoustic set up.https://www.instructables.com/answers/Thermoacoustic-electric-generation-at-high-frequen/ By the way, I am guessing that whatever you are building, you want to start small. That's why I linked to that dollar store junk. Well, that, and I don't actually know where you'd find expensive, high-powered, piezo transducers.