Here Is an Enclosure with Lid for a 12V to 5V DC/DC Converter.
I use the Converter for power the Octopi with the 12V PowerSupply of my Printer.
Its the best Converter i have found, gives constant 5.2 volts and reached a maximum temperature of 40°C. Its Perfect for use with a Raspberry Pi and OctoPrint!
Here is the Link to the Converter:
https://www.amazon.de/gp/product/B071ZRXKJY/ref=oh_aui_detailpage_o00_s01?ie=UTF8&psc=1
or
The Converter have no holes for mounting, you can fix it with hot glue or double-sided adhesive tape into the enclosure
*UPDATE: - Changed the Lid because it was not possible to put it on the base after wiring the converter