I'm trying to do something similar with another liquid. A peristaltic pump might work but any pump can take a surprisingly high d.c current and batteries may be larger than the vessel! Also. pumping any kind of 'Gloopy' material is problematic for most pumps. It seems to me you can't do better mechanically than the gel dispenser pump attached to a solenoid? I've not seen small one's, but the motor driven screw type Archimedes pump would fit the bill and finding motors to turn the screw is easy. You just need to work out how to drive the screw with an external motor.