this is the circuit I've come up with so far:
although it has quite a lot of issues already:
-the 10 ohm resistor will dissipate a LOT of power
-the voltage doesn't really reach -12V and is not regulated
I'm not sure how to add another stage to increase the output voltage to about -24V, then I can use the LDO to reduce noise,improve load regulation etc.
Also I'm not sure how to increase the output power. 2 things that I found that help are:
-increasing C2 and C3 capacitor values
-reducing R5
but R5 needs to be an order of magnitude larger (or two orders for that matter!)
capacitor values can be so large without going insane ... 4700uF capacitors are gigantic but I have two on hand so I can use them as a last resort.
I have more op amps available. is there a way to somehow put these circuits in parallel to boost the output current?
Edit: here is another simulation with a 100ohm load (output voltage drops to about 10 volts):