Amazon.com: iUniker Raspberry Pi Power Switch, Raspberry Pi 3 Power Supply Cord Pi Power Switch Cable Switch Push On Off for Raspberry Pi 3,Pi 2,B+,Zero w MicroUSB Female to Male (4-Pack) :
Raspberry Pi Power Off Shutdown Switch Button – Chris Tech Blog
How to Turn Raspberry Pi On and Off
HOW TO TURN OFF RASPBERRY PI PROPERLY : 5 Steps - Instructables
How to Use a Switch to Turn On and Off the Raspberry Pi - Circuit Basics
Dr. Monk's DIY Electronics Blog: On Switch for Raspberry Pi
How to Turn Raspberry Pi On and Off
Raspberry Pi Turn On/Off With Any Remote Control : 3 Steps (with Pictures) - Instructables
Service to Safe Shutdown Headless Raspberry Pi Boards - Raspberry Pi Forums