Pull out the old drawer, and empty the contents from it.
Pull the drawer up and out of the pantry, taking it off the sliding guides.
Remove the railings from both sides of the old pantry drawer with a screwdriver, and put the railings and screws together on a counter.
Measure the width, depth and length of the old pantry drawer. Then purchase a new one matching its size at a cabinet retailer or have one one made by a cabinetmaker.
Fasten the railings you removed from the old pantry drawer to the replacement drawer using a screwdriver.
Fit the railings on the sides into the sliding guides, and push the drawer into the pantry.
Pull the drawer open and push it shut several times to ensure it is properly installed, then put the contents back into the drawer.