You need these two pieces (although it seems they are the same size, front and rear? I do not know, as I only ever bought the one for the fork):
Fork:
TITANIUM Reynolds / Serotta F3 Carbon Fork Brake Caliper OEM Nut Bolt Ouzo Pro
Rear:
Titanium Serotta Rear Brake Nut Bolt for Meivici Ottrott Nove Fierte iT Frames
It looks like the fork nut is sold out,
if the two are in fact different sizes, but PM him here or on eBay (I think the name is the same), and he will surely help. Very nice, professional guy when I corresponded with him.