R-TECH Miniature Piezo Transducers with Flying Leads - R-TECH 350704, This 30mm piezo transducer is able to generate a range of audible tones and frequencies when energised by a 12V peak square wave.
Provided it is mounted rigidly, outputs of up to 80dB can be achieved.
R-TECH 350904 Miniature Piezo Transducer 30mm