Here is an **idea** that manipulates the trigger threshold point, by the D-type flip-flop, to terminate the timing cycle early. D3 is used as a low-voltage, low-leakage zener diode. 

Circuit simulated in Proteus.

[![circuit][1]][1]


Normal triggered output duration.

[![normal][2]][2]


Triggered output terminated by next trigger pulse.

[![normal_off][3]][3]

Output can be turned on or off with alternating trigger inputs. 

[![normal_off_on][4]][4]


  [1]: https://i.sstatic.net/bYtlg.jpg
  [2]: https://i.sstatic.net/Eo6Fc.jpg
  [3]: https://i.sstatic.net/ffChc.jpg
  [4]: https://i.sstatic.net/gOQ8S.jpg