I had in the garage a tube of automotive weatherstrip rubber sealant. I used it to patch anything from a wetsuit, snowboarding glove fingertips, crappy Merrell trail boots when the sole separated to backpack bottoms.
It's runny, the fumes are stinky and toxic, better get Popsicle sticks or chopsticks to smear it. It will get everywhere on your hands. It needs a long time to dry. When its dry its solid rubber.
I'm sure there are better options, I can recommend against superglue however because it dries as a hard surface which will crack and break. No bueno.
Alternatively, if you don't mind raiding your lady's nail polish drawer, try the glossy stuff. Some women use it to stop their nylon legging hose from running.
Along that same thought, if you have excess car touch up paint in the garage, it's like nail polish.
Disclaimer. Chemical may have reactions, so test on a small area first, in a well ventilated area. And start with a clean dry pack.