Yea... I hate to say it, but I don't think there's a ready way to adapt this. One thing I will tell you is it is unlikely you will find a working cable that goes directly from USB to 3.5mm. I honestly would try just googling around for your headset and "adapt to analog" or "adapt to 3.5mm". Perhaps corsair support has some suggestions for this?
But yea, I'm drawing a total blank on how you'd do that sort of conversion. The trouble is many of these cables are designed with a basic firmware to understand reading a USB file system, but I don't think they support just passing along the signal.Sorry mate, I'm lost on this one. Hopefully someone else can help you out.