I forgot to mention that they are planted in 5 gallon containers, not in the ground.

I suspect your plant is still fairly small and could be re-potted? If so, you might want to re-pot them in something called a global-pot (earth pot, etc.).

I've also seen folks use wicks (made from old t-shirts, etc.).

You can google it, but essentially what you do is provide a water reservoir and let the plant absorb the water through the wick.

Outside of that idea, a timer and a small submersible/fountain pump ($15) with some drip line and emitters might work. Put the pump in a bucket of water and plumb your drip emitters to the pump and set the timmer to run as needed. You can check out some of the hydroponic and aquaponic setups for ideas. They often cycle them throughout the day because they don't typically use soil. You wouldn't need to run the pump that often, though.

Sometimes a good friend is the best defense. If you have a neighbor who can water for you that would be ideal. If not, maybe a rain barrel with a pump and timer with drip lines could do the trick.

Here is a link that might be useful: hose faucet timers