Amazon.com: Cheerock 1pcs Piezo Pickup Transducer, 3in1 Microphone Contact Acoustic Preamp, 1/4 Inch Self-Adhesive Piezo Pickups Transducer for Kalimba Thumb Piano and Other Small Instruments : Musical Instruments
Piezo Contact Microphone 3 Transducer Pickups with end pin jack for Kalimba Z9B7 | eBay
I tried my DIY piezoelectric pickup/preamp on a piano, and it works! : r/diyaudio