Based on this product's specifications, here are some alternatives and similar models
Magnetic Reed Switch (Side) No name KN-CA52 — KN-CA52 side-mounted kontaktron sensor
Summary description:
Side-mounted magnetic reed switch (kontaktron) No name KN-CA52. Passive magnetic contact sensor designed to detect opening or closing of doors, windows or panels by a magnet in close proximity. Commonly used in alarm systems, access control and security monitoring as a compact side-mounted sensor for discreet installation.