there are a few self watering systems on the market that will water for about a week or so if memory serves me right.. these are premade units that you can order online..
or, you could set up your own rez and get some pumps and tubing and some timers that you can set in small increments, and rig up your own drip system...
it will take a bit of tweaking on your part to figure out exactly how long to set the timers for and how often to run them, but once you get it all dialed in, you could feasibly leave your plants for as long as you have water in the rez for..