Good luck finding a replacement in the hardware store or even through the original manufacturer. Times like this call for a little ingenuity and craftiness. Enter the Cookie-Cutter Sugru Method.
What You Need:
2) Wax Paper (optional, but it helps the Sugru not to touch food-prep surfaces)
3) Rolling Pin
4) Toothpicks or Kebab Sticks (same thickness as you intend your seal to be)
5) Cookie Cutters or Scissors
Step 1: Preparation
Place them on a flat surface like a cutting board.