broken pro tool tightening handle ?

Hi
Was hoping someone could help
I just brought a secondhand PRO Mitre saw CLM250LSMS with a stand and I need the mitre angle tightening knob with the screw threaded bar
I did not look at it in depth as the bloke had it in the back of his car
He was an older guy and seemed genuine when he told me it was in full working order and had brought it just to do his decking and no longer needed it.
So I was pis d of to find that he had lied as after lugging it all upstairs off the pavement it is missing an important part
It's the part that you loosen to vary the mitre 0 - 45 degrees and tighten to keep it at watever degree.
The screw thread is still running into the body and the washer is hanging on the end but the metal has sheared so beyond there would have been the knob to tighten it in position.
You can see indentations in the aluminium where he has tightened at different degrees,before so he knows what's happened
I am a dumb ass not looking
If anyone has or knows where I can get one it would be a great help
Thanks