The # is 1-800-334-0852 Ext 7 for customer service. Brownell's probably has it - they have the .050" cup pin punch, too (The front sight is pinned.). You'll need a drill bit and pin vise, too. That front sight is probably ~.250". You'll need a new sight windage screw and nut, too - they are generally not serviceable upon removal (rear sight). Brownells, besides aftermarket, also has S&W parts - if you don't have their catalog, and you aren't going to FOP Range today (There is one in the 'Liar's Lounge' there.), go to their website. My h-l 5" 686+ is fun with it's original HiViz & V-notch.
Stainz (John)