You need to replace and solder a FFC connector? I hope it is 1mm or bigger. It is not for the faint of heart. This is dense stuff.
It is possible -- some have done it. First tell us the pitch and the number of pins. Count the pins, measure the width of the cable (in millimeters). Divide. It should be 2.0mm, 1.0mm, 0.5mm, 0.4mm, etc. -- an even number like that.
For the stores selling these, well digi-key, mouser, future or any other electronic supplier. You can also buy a pack of 10,000 on a tape reel.
Watch that it is the same mechanical specs. In particular, that the contacts are on the same side (top or bottom). Else it will not work.