My previous Ford's handbrake had rubber partition that was supposed to fill that gap, but did so ineffectively. My solution was to pull up the center console and attach black felt to the underside. I took a long rectangular section and ran a slit down the middle. Then created significant overlap between the two halves using a couple of tiny safety pins. It was attached to the underside using cyanoacrylate adhesive. Felt can collect dust and if you eat in the car at all, (I don't), food particles. Any arts/crafts and textiles store will have felt fabric for purchase. You can layer the felt to achieve the desired thickness and rigidity.