Amazon.com: MS-2, Reflector, W40.5 X H60.5 X L8mm, Retroreflective Photo Sensors : Electronics
Amazon.com: 3.4“ Round German Reflector | Silver Mirror | Flat | Plastic | for USE with POLORIZED Super Retro-Reflective |PHOTOELECTRIC SENSORS | Photo Beam Sensor | Very HIGH LUMINANCE Factor 6000 X : Industrial & Scientific