Andy, I've been flying gas since 1982 and have never seen these gaskets sold separately. You might check with Champion customer service and see if they will sell or give you a small bag of gaskets.

The first time you tighten a spark plug, the gasket flattens. Many times I have pulled a plug to look at the color and have never had a problem getting the gasket to re-seal. Just make sure the seat on the head is clean.