I'm not in AA so I don't totally get the thing about a need for a higher power, but in general, couldn't you just say the higher power is the possibility of a better you? According to Sartre, when we make choices, we are thereby deciding what we feel the best possible course of human action should be. With this comes responsibility to make choices that will shape the world we want to live in. Given that, can't you just envision a better, sober you as your own higher power? I really don't see why not.