Note the voltage (V) and Amperage [Current draw] in A or ma of the lights. One Milliamp (ma) is 1/1000th of an ampere. Then, search for a power source than can deliver the voltage and current required to power the lights. A higher voltage will cause the lights to burn out faster. A lower voltage will cause the light to get dimmer. A power supply that does nto deliver sufficent current may overload the power supply, cause it overheat, or damage it. Having a power supply that can deliver more current than the lights need is not a problem.
With this in mind, you have several options to power them.
1) If the voltage of the bulbs is 5-6V or 12-14V, you can connect to the +5V or +12V from your PCs power supply. Just make sure it delivers enough current, with the motherboard, and other compents you are running. An unused Disk Drive power connector is the easiest way to go.
2) You can buy adapters from Radio Shack, Target, Walmart, Fry's Electronics, and many other stores that output between 1.5V and 24V, with 1.5V, 3V, 4.5V, 6V, 9V, 12V, 15V, 18V, and 24V being most common. Just make sure the voltage and current correspond to what the lights need. With Incandesent light bulbs, it does not matter if the voltage is AC or DC.
3) You can also take a look at your junk box, and sometimes you will find adapters from old devices you no longer use, such as toys, answering machines, and other devices. Many of these can be used, as long as the voltage and amperage correspond to what your lights need.