When I bought my Dell Vostro 200, a Dell A525 2.1 Speakers with Subwoofer (313-5672), it came with one three-prong cable that had a 9 pin out of the sub, with the two desktop speakers hard wired into the cable.  I have since replaced my desktop speakers with two much more reliable and performing Roland speakers, but I want to continue to use the subwoofer that came with the original system. All I need is a MONO DB9 pin male to a 3.5mm mini phone jack for the back of the UPC into port #4, which is  specifically for a subwoofer, but I have spent days on the internet trying to find such a cable and it seems none exist. Can anyone help me with this simple yet impossible problem? PLEASE!!!