Suggest you check out www.stormsure.com : this is the site of a UK company that makes an excellent boot-and-fabric repair/adhesive thingy-in-a-tube. It’s like, say, Shoe-Goo, or Plumbers’ Goop, but less viscous.
So far, this is unquestionably the best such product I’ve used. (I’m 64, been riding motorcycles since I was 17–you do the arithmetic. I also hike, ski, canoe — not all at once, and not in the same place.)
My experience with this item: This past summer, my daughter & I were hiking in the Spanish Pyrenees. It was late July, but we met Scottish weather: two-plus days of constant rain. The trails turned into streams. C’était pas fun, as we say in Québec. We did a day in constant rain, 10 hrs on the trail, up 700 metres to a pass at 2900 metres, then down 1200 metres to the refugio. I was wearing my very good quality Sportiva hiking boots, which had seen me through some very tough and wet terrain in Southern Africa, the Rockies, the SCottish highlands, and the Adirondacks in upstate NY. BUT, over the years, I had seriously abraded the leather on the outside of my right boot, above the protective rubber rand — and the Scottish/Spanish streams-posing-as-trails soaked my right foot completely. C’était pas fun, pas du tout, not at all.
So, we dried out after staying an extra day at the refugio, and changed our plans: we aborted our through-hike so that we could fix my boots, and took the bus to Torla, a small village near the entrance to the Ordesa Canyon Ntl Park. Sublime place, and by now, it was sunny and dry. Torla has several mountain shops. We went into InterSport; I described my problem with my boot, and they sold me a tube of the Stormsure adhesive/repair plastic-in-a-tube. Turned out to be absolutely brilliant: squeezed on in a not-too-viscous-but-not-too-runny-either stream; I spread it out with a twig, carved flat, thin & flexible with my Swiss Army knife, and the Stormsure dried in two hours, and cured fully overnight. I used my boots that days, and put on a second coat that evening, covering a larger surface. The Stormsure remained more flexible than, say, Shoe-Goo, and held up with no problems at all in a further ten days of hiking on rough and rocky trails. No rain, but this stuff effectively gave the abraded section of my boot a double layer of durable flexible plastic covering. I hosed it down at home to check–no dampness inside, none at all.