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

https://de.aliexpress.com/store/product/Replace-LM2596S-DC-DC-24V-12V-To-5V-5A-Step-Down-Power-Supply-Buck-Converter-Adjustable/2130127_32803394960.html?spm=a2g0x.search0104.3.8.40002d1eipUUrF&ws_ab_test=searchweb0_0%2Csearchweb201602_2_10320_10152_10151_10065_10321_10344_10068_10342_10547_10343_10322_10340_10548_10341_10696_10084_10083_10618_10304_10307_10820_10821_10302_10843_10869_10868_10059_100031_10319_10103_10624_10623_10622_10621_10620%2Csearchweb201603_44%2CppcSwitch_5&algo_expid=0f655fe3-7320-42f1-98b6-0912b9ad1c30-1&algo_pvid=0f655fe3-7320-42f1-98b6-0912b9ad1c30&transAbTest=ae803_1&priceBeautifyAB=0

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