uhm.. here in Italy we have a 3 prong cable like this connected to the adapter brick of the Thinkpad (sorry for the very long link)
so, if in the US is 2 prong I will need a different solution
Your 3 pin cable uses a C5 connector. All you need is a cable with a C7 connector, which is 2 pins. They are very easy to find, and very cheap. You might already have one somewhere in your house... I use this kind of cable for my laptop psu, my camera battery charger, my printer, my scanner, and my external dvd drive and many more devices. These cables are virtually everywhere. Lots of electronic devices use them.
Look at the C5 and C7 connectors on the wikipedia article for IEC_60320.http://en.wikipedia.org/wiki/IEC_60320