NMD XR1 Triple Black fabric tear repair?

After 3 months of using my NMDs, fabric tears occurred on the inner soles of both shoes: http://i.imgur.com/J8viH9i.jpg (Didn't clean them as I don't use them ATM since it's winter, sorry!)

I asked Adidas about it, they said they can give me a gift card in exchange for the shoes. Since this shoe is not sold anymore, I'd rather fix it.

Any thoughts on the best way?