Have you searched around for a DB15 female to female cable? You could always get a male/female cable and use a gender changer. You can also make your own, which wouldn't be too difficult with some basic soldering tools.
I'd say roll your own, too. Console5 has cheap extension cables you can splice, or for those with less technical skills (like myself), an extension cable + another NG cable with one end stripped + a DB15 breakout box. Better than 5000 yen charged above where linked.