Based on this product's specifications, here are some alternatives and similar models
Reed Switch / Side Contact Sensor No name KN-CA51 — KN-CA51
Summary description:
KN-CA51 is a side-contact magnetic reed switch sensor (brand: No name) designed to detect opening or movement via magnetic field interruption. The compact KN-CA51 fits flush mounting at door or window frames, provides simple normally open/normally closed wiring compatibility, and is suitable for alarm systems, security sensors, and basic magnetic detection in residential or light commercial installations.