does anyone know of a npc locator addon? or can possibly make one?

I don't think it's possible to make such an addon, unless you're looking for mobs/NPCs that are stationary (don't move, very much or at all). If that's the case, then you can use something like Cartographer or MetaMap with map notes/waypoints =)

But making an addon which tracks NPCs in realtime, is unfortunately not possible as for now; addons can only interact with the 2D interface, and not with the 3D world (except for getting information from it, through the Combat Log)