Can confirm the left hand end of the brake adjuster rod has a right-hand thread with a standard (for BS) 5mm x 0.9mm pitch JIS thread, nut is 9mm across flats. Current ISO nuts have 0.8 pitch, 8mm A/F. I would buy a tap and rethread an ISO nut. Taps are cheap and will come in handy .
Of course, Richard may have the correct nut.