Instructions
Decide how much you are willing to spend, and then look for chess clocks in that price range.
Choose between a digital or analog chess clock. Both types of clock function in the same way -- each side has a timer, and one side ticks down until a button is pressed, indicating the turn has ended. This freezes the clock that was previously ticking down, and starts the other player's clock. The digital or analog debate usually just comes down to preference, since you will likely be able to find both varieties in your budget range. Digital chess clocks have the small added expense of purchasing batteries over time.
Select an online vendor for your chess clock. There are numerous merchants available online who offer both digital and analog chess clocks. Check a variety of retailers like Amazon and eBay, but also be sure to check out specialty merchants who deal only in chess supplies. When you are comparing prices, make sure that you are comparing the same makes and models to one another.