Add a new zipper slider yourself by removing the existing one and replacing it with a completely new one instead of deeming the garment unwearable. Zipper sliders come with a size number located on them for identifying and matching the size needed for replacement. You don't have to have experience being a seamstress in order to do the zipper repair either. Replace your broken zipper slider by removing the old one and attaching a new one in under an hour.
Acquire a zipper slider that matches the one that's broken. Locate the size number that is embedded on the zipper slider and find another with the same size indication at your local fabric supply store.
Remove the old zipper slider. Use the seam ripper to carefully cut the stitches that hold the fabric at the bottom of the zipper tapes, and then use a sewing needle to reveal the base of the zipper track from underneath the fabric.
Guide the new zipper slider onto each side of track teeth evenly from the base and pull it upward toward the top. The tracks feature longer pieces of metal than the rest of the tracks at their bases for insertion purposes. The track teeth will now be in locked position, intertwined with each other, and the zipper will now be closed.
Reattach the zipper foot by sewing it to overlap the track tapes with needle and thread as it was before detachment. The foot refers to the area at the bottom end of the zipper track, which is located furthest away from the space where the zipper is designed to sit in its closed position.
Guide the bottom of the zipper track into the fabric base using your sewing needle if you experience difficulty when reinserting it back into place.