ps: If the 0V point between +9V and -9V needs to be referenced to the 0V point of the 24V supply, then you will need at least one SMPS.
ps: In the suggestions below, I'm assuming that the 24V supply is floating with respect to the 0V point between the two 9V supplies.
You can use a LM7809 and a LM7909 if both of these are still available. At 1/2A you will need big heatsinks. Or use a positive adjustable regulator like a LM317 and a negative one like a LM337.
Alternately, you could use a single 18V regulator with a power opamp to split the 18V into half. The output of the opamp defines the 0V point between +9V and -9V.