Fulcrum RT-013 fixing "Screw"

I’ve sourced a 2010’ish Cube Agree GTC with very little use on Easton wheels.

Long story….. but I wanted to replace the noisy freehub and have sourced a new Fulcrum RT-013 unit. However I’ve lost the screw that locks it in place – its an externally threaded hollow "screw" that fits in from the non drive side and nips the static part of the freehub into a "splined" recess, machined into the alloy wheel hub ( driven by a large hex / allen key)

Ive searched various websites / exploded drawigns and cant find it so am struggling to source a replacement – either new or used

Pity as the wheels are otherwise in excellent condition and I’ve just spent £40 on a new freehub!

Does anyone have a part number for this item or any suggestion of how to source ….