Canon EF Screw CB2-0397
Canon CA2-4585 EF Screws
Canon XA1-7260-559 EF-EF-S Screws
Canon CD4-2984 G10 Screws
Canon YA2-0929 EF Screws
Genuine Canon collar retaining screws for the collar used in the EF 70-200 2.8 L USM, EF 70-200 2.8 L IS USM, and the EF 70-200 2.8 L IS II USM lenses.  Package of 1 screw. Made by Canon Japan.
The collar used with this screw is in stock here.