TPS7A33: Which negative to negative buck as pre-regulator

Hello,

I'm designing an analog board that needs clean +5V and -5V power rail for opamp. I have a +20V an -20V switching power supply as power source. I would like to use the TPS7A33 and TPS7A47 for the final regulation, but to avoid power loss I need a buck to pre regulate the 24V to something like 6V. The preregulated supply will also be used to power other circuit. I need at least 2A continuous on the preregulated rails. What buck/regulator could I use to generate these rails ? There a lot of choice for positive buck, but I don't know the one that can be easily used as negative-to-negative buck.

Thanks in advance