Hi Darwinia,
If you're committed to the 12-step approach, there are some resources out there on this question. One that I found helpful was "A Skeptic's Guide to the 12 Steps" by Philip Z. (I have no financial interest in it, just found it helpful). Kevin Griffin also has a number of very helpful books about Buddhism and the 12 steps which are not particularly religious, but have a long discussion about how one can conceive of higher powers. "A Burning Desire - Dharma God" is one of them.
In my experience, there is a rational path through the 12 steps if one is so inclined.