What Size Screw is this inside my 6800 Ultegra Shifter

Wrote the majority of my bike off recently. Salvaged the bits which still function, and when I took the shifters off, which are fine, I realised about 4 years ago I lost the tiny screw circled on the diagram when I took them apart to get the frayed end of a cable out. I wrapped it all back up in electrical tape and it worked flawlessly since.

Anyway, now it looks a bit naff when trying to sell, does anyone know what dimensions that tiny little screw is?