Rich,
Haven't installed mine yet (son has car). I don't mind going to Ace for the lock nuts, but unsure what to get. By "all metal lock nut" do you mean the type that have deformed threads on one end, usually from swaged dimples in the nut, or do you mean a spring type lock washer? The deformed nuts might be hard to find in metric. Do you have an Ace Hardware PN or what tray to look in?