If both apportioned plates are lost or stolen, get from Report of Lost or Stolen Motor Vehicle Items MV-78B from a police agency.  Also get the same form if your items were lost because of a crime.  Your items will be replaced at no fee if the form shows the items were lost because of a crime.
How do I apply to replace IPR registration items at the DMV?
You can apply to replace IPR registration items at the Customer Service CounterRoom in Albany.
What is the address of the Customer Service CounterRoom?