I couldn't find a tool I needed for love nor money so I set out to make one
Brass tube 9/32" and brass rod 1/8"
Grind and file
Bend the rod
Go mad with heatshrink
Guessed it yet
YES its a 3.5mm jack tightener
Works a treat, no more slipping and scratching panels, just make sure the rod sticks out enough to engage the hole in the jack and it can't slip
cheers
FRED