For mountain biking, I don't like shoe covers because of the wet and mud. I use these: Seirus Stormsocks

For road riding and depending on the weather, I use either PI Calien Toes or Descente Element shoe coversI have small feet (38 Sidi) and the folks at TE steered me in the right direction size-wize. I couldn't find shoe covers small enough but these fit well.