Any advice for covering/repairing the padding on the heel of these shoe?

I have this pair of vans I bought second hand and so washed by fully submerging them, not thinking about the leather backing which dried out and flaked off. Any ideas for covering it so the cushioning beneath doesn't erode further?

I've tried hand stitching something over (too thick even with a tapestry needle), as well as duct tape, gorilla tape, fabric tape, and gaffers tape without much luck because the tapes will adhere well to the padding but not the stuffing and/or not the other tape.

I'm open to anything because I love these shoes and intend to keep wearing them.