You can buy 12 volt pumps and timers at
Aquatic Eco-Systems, Inc. and then buy one of those car batteries solar chargers to keep your battery charged. Or buy a store bought automatic watering system for about 60 bucks from
Worm's Way - Gardening Products, Supplies, Service, Support, and Knowledge Base for all your hydroponics, indoor, outdoor and organic gardening needs, year 'round! that will water up to ten plants for 3 weeks. You will have to adapt it for hydro because it is for dirt pots.