Faulty DC Power Extension Cable for DK138 Auto/Air Adapter

I use a Dell DK138 65w Slim Auto/Air AC Adapter for my Inspiron 700m. Until recently the adapter worked fine, until it stopped providing power (regardless of source - wall or car). I discovered that the 5 foot DC Power Extension Cable was causing the Output Power Circuit Protection to trip in the adapter. I disconnected the extension and reset the circuit protection by re-pluging the adapter into a wall outlet. The adapter works fine without the extension cable. But the result is a much shorter run than I need.
I contacted Dell and was told I cannot purchase just the Extension Cable. Customer Service said I would have to purchase the entire DK138 kit. Not feasible.
Does anyone know where I may be able to locate the 5 foot DC Poer Extension Cable?
I read somewhere that many times, the problem with the cables is that the thin wires eventually break near the connectors due to wear and tear. I'm no electrician by any means, but I'm guessing that if the cable is causing the Circuit Protection to trip, then there must be a short in the cable - possibly near the connectors where the cable bends most frequently. I want to try to repair the cable. I'm hoping that if I can replace the connectors, this would solve the problem. But I can't find just the connectors.
Does any one know where I may find these specific connectors? I've learned that they are proprietary - Dell uses a 3-wire lead in this particular design. The male plug is 7.4mm OD/5mm ID barrel connector.
I have been able to find replacement cables with the male connector attached that are used primarily on the PA-12 Family adapters, but the oppsoite end are loose wire leads. As of yet, I haven't been able to find the female connector. If I could, then I could simply solder the connector to the leads on the opposite end of the cable. But no luck. The only other option would be to open up the adapter and replace the short DC Power cable run with a new longer cable. Unfortunately, my understanding is that the adapter itself is heat-sealed at the factory, so opening it would be a pain.
Does anyone hae any ideas or suggestions? I've already searched ebay with no luck. I can only find complete DK138 sets which I do not need.