AgCl is very insoluble in water. As I understand the Ag/AgCl electrode, it's an "alloy" of silver and silver chloride {silver chloride can be fused, and tooled or machined as if it were a metal) and the electrode immersed in a solution of some other, soluble chloride. To provide come Cl- anion I would use just about any chloride, NaCl is cheap, KCl is a tiny bit more soluble, HCl is used also. But there is little, to no, AgCl in solution.
Silver does from a complex with ammonium, so as you add NH4OH, you gradually precip. Silver Oxide, until you add a great excess, then you'll have a solution of the silver ammonium complex, [Ag(NH3)2]+, and the counter ion could be chloride, but that might not be what your application requires. What else can you tell us about your app?