I've been helping a friend of mine who is having vision problems with audio books. One source they has been very happy with is
GraphicAudio. Their audiobooks are on the expensive end but they use a cast instead of a single/dual narrator. My spouse and I picked up a omnibus version of Ilona Andrews' Hidden Legacy series (first 4 books plus the novella between 3 & 4) as a birthday present which cost us ~$80 US.