You can try a tube of Vinyl Weld.(Not sure if its evo stick or loctite these days) I used to see it in all the DIY shops but for some reason I couldn't see any the last few times I've been in.
It may or may not work, but is worth a try. I used it effectively on the rear screen of a sportscar hood which developed a small crack.
I reckon it will work . I had a tear in a "window" in a tent , went to local camping shop who supplied spare transparent vinyl and adhesive .Worked a treat .
Hi, I used some of this clear polythene all-weather tape to repair some holes in a tarpauline, after 6 months it was still well stuck, and in better nick than the rest of the tarp. I think it would be good reinforcement to a glued repair.