Other than the large LR slide, there is enough unused fabric to cut the used off and sew the cord back in...can’t just reverse as the diameter of the cord is different on your Septer. Usually it’s the thread that goes bad so have all 4 sides re-sewn while off. Some rollers can be pinned from the end and some have a hole in the roller that you put a nail in once you unroll it all the way before taking one end off so you can slide the fabric out of the roller. Local canvas shop charges me $120 to re-sew all 4 which I remove from on top by myself.
I will also recommend Stone Vos, Just received my new slide toppers and awning fabric from them. The quality is above and beyond any other fabric I have ever used. The customer service is second to none. Give Ingrid a calll you will not be sorry.
You might not need to replace it.. Often there is enough fabric on the roll you can simply reverse it Extend the slide. Pin the roller (You will need to find instructions for that) and bring slide back in a bit, You can then dismount the roller. On the body end you may have to remove a screw or two and "Spread" the channel a bit. then slide the thing out or pull the rib and pull it out (id' slide rib and all. or to be more precise I did) unroll fabric. but body end in roller. put roller end in body and reassemble. If there is enough fabric, if not ... take old fabric to RV store or other (Canvas tarp) store and they can provide replacement.