Get per process user and system CPU time on OSX via command line?
Not sure the information you are looking for is accessible so easily. You could try ps

$ ps -p 407 -o pid,time,utime,etime,comm
  PID      TIME     UTIME     ELAPSED COMM
  407   2:08.23   1:46.36 11-17:10:27 /Applications/Aquamacs.app/Contents/MacOS/Aquamacs


and calculate the system time (TIME - UTIME) and the percentages. This is just the total since the process started though, not an ongoing sampling.