Blueskull: Wtf?
Almost every buck converter can be used as an inverting converter. Because it doesn't matter, if it makes 3V from 5V, or -5V from 5V. Either way the output voltage is lower, that input one. (Input voltage is the Vin+Vout, output just Vout). So I have correctly suggested a AOZ1282 for the job.
Just connect the input voltage to input +V terminal, the output V+ of the buck connect to input and output GND, then you get the negative voltage from the former GND of the buck converter. (In fact, this way the buck converter becomes wired as a textbook inverter).