4-40 Safety Lock Kwik-Link (2 Pack) from Du-Bro - 817
The Safety Lock Kwik-Link offers everything a modeler could want in a clevis and more. Simply put, it's ingenious, a grandslam!  Super strong, super tough. More strength then you'll ever need. 10% lighter than steel clevis'. Size stamped on safety lock for positive identification.
Features:

Self tapping - leaving no slop on threads
Square shank for easy installation & adjustment
Brass plated stepped steel pin - no binding on control horns or servo arms
Brass plated steel safety lock slides into groove on pin for a secure and solid lock
Safety Lock is mounted in trac system on clevis to help prevent losing it