Amazon.com: Taidacent Non Contact Liquid Level Sensor Contactless Water Tank Water Level Sensor for Tank Water Level Control with Low and High Level Output : Industrial & Scientific
28090 Mini Liquid Level Sensor - Parallax | Mouser
3-hole Mounting Fluid Level Sensor | Capacitive | Fuel/Oil | up to 450mm
Fluid level sensor | Aerospace | Eaton
5 eTape Liquid Level Sensor + extras : ID 3827 : $39.95 : Adafruit Industries, Unique & fun DIY electronics and kits