This kit of parts will let you mount Rasperry Pi's (only tested with RPi3s) to a flat surface.
The caps should have enough friction to hold the Pi's down to their plates. I think that I had to drill out two of the DIN rail holes just a bit to fit the anchor screws that I used to attach it to the wall.
The Anker power supply that I used:
60W 6 Port USB Wall Charger,PowerPort 6