[SR5] How to add a weapon focus?
 

I've looked all over gear (where other focus are) and melee weapons (where other melee weapons) are and cannot find weapon foci. Anybody added one of these?

When you add the weapon type you want, use the "Customize" button to add it, or once added, press the Edit button on that item (the button with a wrench and hammer). On the Customize form, one of the options is Modifications. In that list you'll find Weapon Focus among the modifications you can add.