Note the voltage and amperage ratings of the lights in the pushbuttons.
If the voltage is 5-6V or 12-14V, you can run from the PC power supply using an unused disk drive connector.
You can also get adapters from stores such as Radio Shack, Fry's Electronics, Wal-Mart, Target, and others. Again, make sure the voltage matches the voltage of the lights, and the amperage rating exceeds the current draw of the lights. For incadesent lights, it does not matter if the current is AC or DC. However, for some types of lights, it does matter.
Note: A higher voltage will cause the lights to be brighter and burn out quicker. A lower voltage will cause the lights to be dimmer, but will not damage them.
If you know the lamp type
www.donsbulbs.com is a good reference of voltage and current requirments.