I don't have an answer to your specific question and don't claim to know better than Ultimate.
However, I have found that "Shoe Goo" is readily available in many places and I have used it in several applications other than what it's sold for. It is tough and durable and adheres to most fabric/leather materials. It remains flexible when cured.
I'd be surprised if it wouldn't work well for your application if you can't find what you're looking for.
Shoe Goo is marketed as repair adhesive for footwear.
