here is what I would do....take thin CA glue and a toothpick rub it across the crack (remove the lip stop) let the first layer dry and sand with 400 grit....then apply a second coat...and sprinkle some baking soda on it....let it dry and then sand with 400 grit...this will fill the crack and cover it with a snow white appearance...I would also insert a toothpick in the open end of the mouth piece to protect the insides from the glue...when you apply the first Glue pinch it between your finger to seal it good...