From here

You can directly enter the Unicode text for the Narrow, non-breaking space, in Pages v5.

1. System Preferences > Keyboard > Input Sources
   Click the + button and add Unicode Hex Input (this will appear on your Finder menu by the time)
2. While in Pages v5, select this Unicode Hex Input only when you wish to directly input a character
   option + 202F (the letters can be lower-case, makes no difference)