You could build a voltage inverter like
this and use both outputs (+9v from top track, -9v from fourth track). Uses an ICL7660S (the S is important!!) which are common and inexpensive. I bought ten for like $3.
I believe someone in the comments of that post actually did this. It will (should) be exactly what you need.
EDIT actually,
here.
Through all the worry and pain we move on