Water switch for hozelock fitting? Solar-powered watering problem

Hello,

I would like one of those timed water switches that you get for mains taps, but for my hose-lock type fittings.  They don’t seem to exist, but has anyone heard of such a thing?

My reasons: I’ve got a watering system for my polytunnel, which runs off a solar-charged leisure battery and a large tank of rainwater. This then feeds into a number of drippers around the veg. I only need it for when we’re away, when I run a timed watering schedule using a non-submersible pump. The problem is that some of the drippers drip constantly, but most don’t. This means that it wouldn’t work to just let it drip with no pumped watering schedule, because some of the plants would die. But I’m concerned that if I let the pumping schedule run, because of the constant dripping the tank will run out of water. This could damage the pump, and obviously also then not water the plants. I have tried fiddling with the drippers to reduce dripping, but then those ones end up barely running when the pump is going.