Synocean make DC to DC ATX Power Supplies in ±12V ±24V ±48V and ±120V. Most commonly used in Vehicle computer power supply installs these can be 1U 2U or 4U style for the case of your choice.
See the Specs table here 2U 4U Power Supplies or see www.synocean.com.au for full details.
DC to DC ATX Power Supplies in 1RU from Synocean - The leader in Industrial DC/DC Power Supply technology.
1U DC to DC Power Supplies.