If you want a zipper find one thats about 5 to 7 inches long at a craft store, then slit the back of the head with a razor blade and i like to make it a little circle at the top so it wont go tear anymore. Then you will need to get a realy heavy needle and thread and do some basic sewing of the zipper into the latex. (probably need plyers to get it through) Once its on there cover it in latex to help hold it in place and make it strong. My humble opinion...