I just made that repair myself. Fortunately the "rip" was just an un-threading and I did not need new parts.
After checking with several boat upholstery repair places all were too busy to make the repair in a timely manner. I ended up stitching it back by hand with a heavy needle, pliers and 100 lb test fishing line.
I started out with dental floss but found it not substantial enough.
Tedious and time consuming, it took about 4 total hours - but it worked.