What does the screw do? You say it's missing and not gripping? What is it not grippinhI bought this off a forum member a while back, so having just taken a deposit on my 300c it's back up for sale to forum members.
Wiring harness etc included
Only slight issue is I think it was sold to me with one of the screws not gripping - this never bothered me as a strip of tape round it was more than sufficient.
Collection welcome - just outside Glasgow.