Voltage regulator IC with positive and negative voltage output
You could do it, for just a few milliamps, with two zeners and a resistor.

If you did it this way you could probably get away with a 1206 SMD resistor (0.5W) and a dual series SOT23 zener, in total smaller than most linear regulator packages. Here is a possible circuit (output is 9.1V per rail):

      ____
48V -|10k_|-+-- 9V
            |
         |__|__
           / \ |  9.1V
          /___\
            |
            |
            +-- GND
            |
         |__|__
           / \ |  9.1V
          /___\
            |
Source COM -+-- -9V