120 volt applicaitons?

If the switch has a 12 volt incandescent light in it, you can use a small 12.6 volt filement transformer to convert the 120 VAC power being applied to the flourescent lights to 12.6 VAC for lighting the switch (AC or DC doesn't matter for incandescent lamps).  If the switch light is actually an LED, you will need to put a diode (like a 1N4007 in series with the transformer output. 

You should be able to find a suitable transformer in Radio Shack.     

Here's a link for a transformer...

http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F011%5F002%5F016%5F000&product%5fid=273%2D1365

Of course, it might just be simpler and cheaper to replace the switch with something using a 120VAC neon light (if a lit swich is important to your application).

If you want, you can use a relay with a 120VAC coil.  Just wire the coil of the relay in parallel with your flourescents.  Wire 12 VDC through the N.O. contacts of the relay to the light in the switch.  Here's a link to a suitable relay from Radio Shack...

  http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F011%5F002%5F013%5F000&product%5fid=275%2D217