The larger of the two 'normal' plug sockets in my cheap 'Halfrauds' socket set fits, and it has a rubber ring in it that stops the spark plug falling out of the socket too. Mind you, I bought the set twenty years ago, so that information might not be much use. I imagine the smaller one is for motorcycles or lawnmowers or something? Hope your friend gets lucky.
What happened to 'Lucky'? Haven't seen you round these parts for some time.