This is my understanding of it. All auto manufacturers have usually one plant that makes small production runs of things, think injection molded parts or specialty machining processes required. GM for example still has molds from things they produced in the 80s sitting in a warehouse. Occasionally they pull things out for one off runs of less than 50 units. Chrysler does the same thing, they used to make one off productions of our Dash components of 100 or less units for the year to distribute to various resellers and their own warehouses. Some things are replaced entirely by aftermarket suppliers.
That being said, manufacturers stop production of certain parts of vehicles shortly after production of that model ends. In this case i'm guessing production of the striker was stopped a long time ago as it shouldn't rust out before the life of the vehicle is up, or unless its in a serious car accident, in which case the vehicle may be totaled. If the dealer cant find it, i'd ask them who they send the collision repair too and call that place directly, the dealer can get most body products, but not always.
