Hi
I use an ATXRaspi in mine with a non latching switch. I got mine from here
http://lowpowerlab.com/atxraspi/
Photo below (the small PCB behind the top right corner of the Pi - not the one on the GPIO)
https://forums.pimoroni.com/uploads/short-url/mykXR4s6RmOuuxLMZV8nCw99oWq.jpeg
Other folks use the PowerBlock available from here
Cheers
Paul