Just for interest, to complete the story
Following John's initial response (thanks John) plus some rummaging in Parts Lists (thanks Ash) and a bit of Googling for good measure it seems that the bracket P/N is 84701-323-600B and it only fitted to 500/4 K0 and K1 UK models and 750/4 K2 UK models.
Now sold to James's mate for his 750 K2 rebuild.