I picked up one of these the other day to simplify the power wiring in my cabinet and I'm extremely happy with how it works...
Digital Loggers IoT Power Relay
https://dlidirect.com/products/iot-power-relay(I actually purchased mine on Amazon because the shipping was more reasonable [free with Prime])
I picked up a push button switch from radio shack (see below) and mounted it in spot where my cabinet originally had a toggle switch. I wired the switch to my PC on/off button. One press of the button turns on my computer, another press shuts down my computer. When the PC turns on, a USB cable from my PC triggers the IoT Power Relay, which switches on my cabinet power (monitor and marquee). When the PC turns off, the IoT Power Relay turns everything back off.
Momentary Pushbutton Switches (2-Pack)
Normally open. Includes one red and one black. Pkg. of 2
Catalog #: 2750609
https://www.radioshack.com/products/pk2-spst-push-swNote that the IoT Power Relay has a socket for a standard PC power cable (C13) and it ships with a cord but it's only 12 inches long. I'm using it as the primary power source for my cabinet so I ordered a 12 ft C13 cord off of Amazon. There's tons of them available in almost any length you could want.
Here's a video that shows how you trigger it with power from a USB cable...