We have an older car that has developed a perpendicular split on the left-hand driver's seat (US car) about 4-5 inches long. I have a thin kidskin leather made into a jerkin-styled top, which I no longer wear. I had Fred pull it over the headrest and let it fall without tucking it in. It worked very nicely, until his constant sliding out of the car tore that also. I can repair the split, but believe it will just rip further along. So, what in fabric or leather, would be a good choice? No vinyl, it is too difficult for me to handle.
Sorry Jimmy. I don't think there is a way to repair a split in leather other than replacing it.
Actually, you can repair a cut or rip in leather. You may have to go see your local cobbler to get some contact cement used for leather (I prefer Helmitin or Renia and dislike Barge). Skive * the edges of a patch and glue it on the back side of the affected piece, flesh side to flesh side. I like to apply it while the glue is still wet so I can adjust it a little to get rid of wrinkles. Turn the project over and use a needle or skewer to put a little glue right in the cut and then adjust to where everything is flat and aligned. Any glue that seeps out after you press the patch on can be removed from the grain side of the leather with an eraser after it dries.
* skive = bevel the edges. Put the patch on a smooth hard surface like a piece of marble or plate glass and cut with a sharp knife from 3-4 times the thickness of the leather to 0 at the edge. or sand it off on a drum sander etc...