A lot of people clicker train their dogs. They are a great way to pinpoint the action you want to reward. They act as a bridge between the reward and action.
A generic clicker can be found at most pet stores for little or no money. Here is also a source for them.
Some dogs are somewhat sensitive to the sound of a clicker, so people wishing to clicker train may have to resort to some other noise.
This place sells “quieter” clickers.
Or you can make a click sound with your mouth.