Lowe's is where I got mine.
The ones I have are from Intermatic, it's an astronomical digital timer. I don't remember the model, but they were about 20 bucks each.
They have one for about half that, but the reason I like these is that they can be programmed for seperate daily, MTWTF, Weekend, etc settings. I have my lights set up to come on a couple hours earlier on the weekends so I can enjoy my tanks for more time. It also allows for a whole bunch of cycles per day, so if you are running pumps or whatever you have that flexibility.
Supposedly they are astronomical too so they can follow sunrise/sunset times throughout the year, but I have yet to try that feature.
I looked on their web site and I don't see them there, so maybe they don't have them in your area?? Regardless, I am SURE they carry 3 wire timers of some type.