Found the Soma Junebug which is 31.8mm and looks like it has less drop and perhaps a bit more flare than the new WTB but this review mentions that the clamp area isn't very wide (it doesn't seem like this is specified normally) which would be a problem for the aero bars.

This guy seems to think we'll see some new options in this space in the near future. I'm not in a massive rush so I'm looking forward to it.