Hi - Although I cannot answer your question directly, here is a link to a web page which helps determine which manufacturer vent is installed; take a look at the hinge style on the vent to determine if it is Jensen, Elixir or Ventline. THis helped me in the past.
Link to Vent Cover Hinge and replacement covers.
Then you can determine your preference for material of construction and order from a vendor you choose.
Hope this helps.
Here is a link to another all inclusive RV vent distributer -->
Link
Take care,
Brian