I came across this earlier: https://www.ebay.co.uk/itm/324793265456?hash=item4b9f2fed30:g:d6gAAOSwBHhhRHvU But wouldn't be reusing that nut of course.
I'm not sure the number etched onto the flywheel in the image is the part number, but it's not exactly cheap enough to take a chance really.
