ORIGINAL: cajun1
Apparently these were available commercially at one time, but I suspect they were for 14MM plugs, as they are still available. No one I've found has the 10MM X 1/4-32.
C&H is closed forever.
I do have some 10MMX1/4x32 adapters left over have about a dozen of them.$5.00 each plus $3.50 P&H .Just send me a check and number you want plus P&H.
I do not have gaskets for the 10MM side.You can use a gasket from a 10MM CM-6 spark plug,hard to get off.
BCCHI