Vampire fangs are in accessories, right below socks. They're recognizable by their icon, which is a closed mouth. You can give them to any sim you please, or remove the from your vampires in case you want them to go stealth. They're Create-a-Style friendly too, but previewing fangs in CASt is a bit of a pain.
The neck marks for vampires are right below the fangs, just in case you have the urge to edit those or remove them from your vampires entirely (like I do).