Build your own. Helluva a lot cheaper, and more configurable for what you need. All you need is a cheap spout timer, some drip tubing, and a couple connectors. Any hardware store will have all the bits and pieces you need, but there are tons of supply sites online that can ship any bits you need.
You can what a kit looks like here for example. You could just buy a starter, or source the bits yourself for a little bit cheaper. Once you have a basic setup going, it's dirt cheap to maintain and build off of in the future.