Go to:
http://www.allelectronics.com/cgi-bin/category.cgi?item=DC-32&type=store&review=all and buy this part, it's only $.99 Now, there has been a lot of confusion and problems getting this part to work. I have made 10 of these so far, and it takes about 30 mins tops to make a solution. It is a stable, cool running, and solid solution to getting negative voltage for contrast. Follow this diagram I made, it is simpler to follow than the supplied schematic with the part:
I hope this helps. It is very easy to make, even if you dont have much soldering/wiring ability. Any quesitons, please feel free to ask.