Amazon.com: 3D Printer Parts Filament Detection Module Detector Sensor Switch Run Out Pause Monitor for Creality Ender 3 V2/CR-10 V2/V3 /Ender 3 Max : Industrial & Scientific
3D Fun smart filament sensor DIY kit optic encoder and grating wheel - Pandaradiz
Adding filament sensor in SKR electronics (MINI E3, v1.3, v1.4 and v1.4 Turbo) - 3DWork
3DPrinter Filament Width Sensor Kit from JasonKits on Tindie
DIY Filament Runout Sensor for 3D Printer Fault Detection using Arduino