Liquid Flow Meter - Brass 1/2 Nominal Threaded : ID 833 : $24.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Usn-hs43tat Ultisensor Hall Effect Sensor Water Flow 1-60l/m G3/4" Water Purifier Water Dispenser With Temperature Sensor Ntc50k - Flow Sensors - AliExpress