I've seen https://www.pi-supply.com/product/pi-su ... er-switch/ which seem to be quite good, but might not work with the Pi3.
Does anybody know of a switch that can be used on the Pi3 as well??Raspberry Pi3 users If you use the Pi Supply Switch with the Raspberry Pi3 you may experience under-voltage issues and unexpected power off.
It does say shorter better quality cables might help, but what have other people tried??