Let's say we have a power supply that puts out +3.3V and -3.3V at some amperage. We also have access to a boost module, such as **broken link removed**.
It's obvious we can use the module to turn +3.3V into +5V. Can it be used to turn -3.3V into -5V?
If your ±3.3VDC supply will go to +10VDC, you could construct this OpAmp based dual supply (virtual ground) generator:
R3 & R4 are just dummy loads to demonstrate current capacity (TL081C will tolerate a 1A load). Also note V1 source is isolated from load ground.
<EDIT> Removed the unnecessary ground from between R1 & R2!
https://www.recom-power.com/pdf/Econoline/R1S_R1D.pdf
In the above data sheet there is a 3.3V in to isolated 5V out at 300mA (you did not say how much power)
The input can be from +3.3 or -3.3 it does not matter.
>+3.3 is simple (+) on 3.3V and (-) on GND
>-3.3 = (+) on GND and (-) on -3.3V !!!!
The output is simple. Connect (+5 output) to GND and (- output) to -5V
There are many little power supplies like this from many places.
Look for DC to DC Isolated supply.