In the past, when portable systems were powered, sources (batteries or rechargeable batteries) were combined to increase the overall voltage. Now that DC/DC converters are becoming more and more efficient, let's use them!
I've already explored 12V models from Traco Power, Recom, and Meanwell with success.
For this 5V version, I turned to the Murata NMH0512SC.
It's a 2W module that's fully isolated and compact. Currently, 5V is found almost everywhere (power banks, computer USB ports, even in cars).
For my part, this will be very useful for all my audio circuits that require balanced power supplies.

Here's the schematic:

We're getting 5V from a slow 315 mA fuse. It protects against overcurrent consumption or if the TVS protection diode shorts out in the event of a power surge. L1 & C1 form a filter that prevents RF feedback to the source. C2 & C3 provide output decoupling from the converter.
For optimal results, it is recommended to add a double filter to ensure ripple rejection.

Here are the PCBs:

My design allows them to be placed side by side or stacked with spacers.

However, it is possible to make these 2 modules with pre-drilled plates.
All components are 2.54mm pitch.

When powered up with no load, we measured +/- 20V at the output. I placed two 820 ohm resistors to deliver a current of +/- 15mA (12V / 820r), and then we stabilized at +/- 12.08V.
For safety reasons and to avoid destroying downstream circuits, I placed two 5K1 resistors to create a small load, which could be 2mA LEDs.