I took the Ender 3 Tray that Holspeed created and added a raspberry case to hold your OctoPi. I also put a hole in the back to fit an XT60 connector. I used an XT60 splitter and pulled 24V off the printer and stepped it down to 5V 3A to power the Pi. Now the Octopi and Printer are self contained. This is a work in progress. I may redesign it depending on how I decide to do cable routing.

Parts:

Converter: https://www.amazon.com/gp/product/B00N2G5HKC/

XT60 Splitter: https://www.amazon.com/gp/product/B0179IODB2

XT60 Plug: https://www.amazon.com/gp/product/B01GJ5RCE6