If you use Algarde flexible silicone tubing outside the pole, you won't need any kind of device. Just fold it, stand on it, pinch it, to stop the flow. Ask Jeff Brimble, he put me onto it.
6mm outside diameter, will push onto 6 mm connectors. Buy 100 meters for less than £30.
Best pole hose ever. If you want to stop the flow to take your pole round the back, just fold it and slip a ring or piece of bigger diameter hose over it. Simple, and totally reliable. Dai