You could easily solder the lead back together if it truly is broken. But when I broke my Casio E-125 in a nearly IDENTICAL way... I broke that 4 lead cable's counter-part in the E-125, I flipped the cable around so the lead connections were reversed and the screen came on full brightness, I couldn't control the brightness of the screen, but it came on. So after seeing that I came up with the idea to cut the cable below the point that it was broken and then shave down the covering to expose the leads. This allowed the leads to connect in the correct order. But my lead broke really closely to the orignal location, around 3mm away. I don't know how far down the line your lead has broken, so cutting it might not be the best idea in your case
Maybe you could BEND the cable at the location and, with the blade of a pair of scissors, shave the covering from it so the leads are exposed. You can always use tape to close it back up again.