When I did mine, I looked everywhere for something to use. No luck. As I was driving to the next town I drove past the Honda motorcycle dealership. A light went off in my head, Honda... Japanise... metric bolts... hey... . I went to the parts department with the banjo fitting and explained what I was doing, he said let me look. He came back with a oil drain plug and aluminum crush ring for one of the motorcycles. It fit perfect and has a crush ring to seal it too. I have about 7,000mi on it without a leak.
Sorry, I looked for the package it came in or the receipt, so I don't know what the part number is. Just take the banjo fitting plug with you for them to help them find it.
jc