Where does one obtain a RAREP?
Coded RAREPs (Radar Weather Reports) and SDs (Storm Detections) may still be used to exchange data between radar stations, but for human users they seem to have been superseded by visual displays that provide a more human-friendly visualization of the same information, such as at http://www.aviationweather.gov/radar.  The PHAK you linked to (published in 2008) is likely out of date on this.  (But this is the most recent PHAK available.)

From http://weatherjackwilliams.com/answers-weather-radar/ :


  The NWS Aviation Weather Center (AWC) doesn’t have any links to the
  coded SD/ROB reports, but does link to the Radar Summary chart, which
  is complied from these  reports.


This information is also incorporated into a standard weather briefing for a particular flight plan.  The DUAT system used to provide an "SD (Radar Weather Reports)" section in its briefings, but DUAT is no longer available.  DUATS instead has a section titled "Radar Summaries" in its briefings.