The first suggestion is to note the voltage and amperage (current draw) of the lights. Then, you need a power supply suitable for that. A higher voltage will burn the lights out faster. A lower voltage will make the lights dimmer or not light at all, depending how far off you are. Additionally, you need a power supply that can deliver the current required, and if possible slightly more to not overload, and take in your wire resistance. For incandesent light bulbs, it does not matter if the voltage is AC (Alternating Current) or DC (Direct Current).
Some suggestions for a power supply:
PC Power Supply - if the lights need 5-6V or 12V, you can run from a PC Power supply by connecting to an unused disk drive power connector. Again, check the amperage to make sure you are not exceeding your power supply's capacity.
You can look in your junk box for adapters that are no longer used from older electronic devices, toys, answering machines, and the like. Again, make sure the voltage and amperage match.
You can go to Radio Shack, Wal-Mart, and other places for transformer power adapters. Again, make sure the voltage and amperage match your lights.