As I understand it, (and I may be wrong!), there were two possible choke arrangements; there's the thumb choke mounted by the left switchgear that Darkness mentioned (65540031A), and the earlier button-pull choke, which was mounted under the tank (65540011A).
Your arrangement seems to use the large guide 82911281A,
which I thought was only from the M600, mounted through the yoke. (I wonder if a previous owner fitted a different choke when the original broke?).
The cable that's compatible with this guide has a different part no. 65540021A. (Maybe it's longer than 65540011A, maybe it has a different mounting?).
Of the three, I'd think that the one Darkness mentioned would be the best and I'm sure it could be retro- or re-fitted to your bike.