There's rather a large variation in black acrylic (PVA) paints, some will stick to themselves even after drying so need to be avaoided. I deally you need one which gives a matt black finish, I can't recommend a make as the one I use is only sold in Turkey.

Another option is the invisible meand patches for suits/trousers, I foud some that are self adhesive and very thin, strong and more importantly light-tight. I've used this on quite badly damaged bellows and they are still OK 6 or 7 years later.