My child "soaked" the OEM upper rear mattress of our '84 Westy on our last trip. Upon removal I discovered the zipper slider had disintegrated from oxidation but the nylon coils are fine. The two sides of nylon coils appear asymmetrical as one has one lobe where the other side has two, therefore I was unsuccessful getting a common replacement 3mm nylon coil slider to zip the two sides together. Who supplies such sliders? I'm hoping not to stuff the foam back inside and resort to stitching the zipper opening closed.