Do I need an extra deep old-work box for a stucco wall?
Old Work Box Mounting Accessories Link


Option One: Old-work Switch Box Supports with 2-1/2” Long Legs - Most common technique, though probably not as easy as option 2, which is relatively a new design.
Option Two: Cut In Box "Old Work" Mounting Clips.


These items should never be used to support a fixture.  Strictly speaking, only switches and outlets on a vertical wall, or similar.

I would opt for 2, as it may be easier for those not familiar with item 1 and thick walls.