First, there are plenty of inductors capable of several amperes. So - do not be afraid of 500 mA.
Second, you can use the following designs:
- SEPIC converter (two inductors and two "power" capacitors)
- BUCK (Step-down) converter with special connection (one inductor one cap)
- Fly back converter (transformer and one capacitor)
- Half bridge on 24 V with transformer and rectifier
I would suggest using option 4 - if the transformer is not a problem for you. You can use PCB transformers (they are fine on 4+ layer PCBs). You get both +10 V and -10 V from the same simple circuit.
simulate this circuit – Schematic created using CircuitLab
The P/N and values of capacitors have no meaning. They must be selected based on switching frequency etc.
There are plenty of IC able to control gates of two MOSFETs in such configuration. I suggest switching at 250-500 kHz.
The disadvantage is: the output voltages are not regulated, they are proportional to the input power supply 24 V.
Alternatively, you can use design 2: you design the common step down converter on one IC. However, its positive output is connected to Ground, while its "Ground" is used as a -10 V output.
simulate this circuit
Again, values of components have no meaning.
You can use ready made ICs with integrated power MOSFETs in both cases.