You appear to need a 24-pin ATX connector. It's the newer ATX standard. It appears that Opus makes the new 250w PSU with only the 20-pin connector.
Here's a link to a 20-to-24 pin ATX adapter: http://www.saveateagle.com/wcab460-v...-V78&ovtac=CMP
It's not the only one out there i'm certain. It should at least give you a jumping off point.