Hi there,
I’m looking for a door sensor that would be waterproof/weatherproof to use on garden gate.
Is there any sensor that could fit out of the box ?
I’m considering encapsulating an indoor sensor inside a waterproof housing as a work around…But if a solution is already available, I would be happy to know about 
I’ve done that with the Xiaomi Aqara door/window sensors. It’s been working for about 18 months now, but accessing the button on the sensor is inconvenient if a device needs to be re-paired to the coordinator.
Did you 3D print the casing. If so, could you please share it?
I have succesfully used plastic spray for outdoor devices.