I just took some of the front end of my top apart, trying to see if the tension cords that are under the web straps on both sides could be accessed without removing the front portion of the fabric top from the frame, it can't be done without removing the front section of the top from the frame. These two cords are between the front cross member and the first cross frame that the top sides into from one side. The front of the cable is attached to a spring at the front cross member. I believe they usually break at the back end, which if that's the case, they can be pulled back through the attachment hole and then a knot tied into the cord. The cord will have a little more tension on it, if it's shortened but shouldn't be a problem.
I haven't seen these cords sold anywhere, but wouldn't be to hard to create one, if the break is not towards one of the ends.
The picture shows the tension cord that's located under the stay pad (web strap).