[The Bus Crew]

I noticed the roof vent on my bus has no flap to close the vent, I am not sure if it never did or it was broken at some point in time.  I would like to make what I have function as I like the vintage look of it and the fact that it is all aluminum on the exterior.  My vent has 3-T's stamped into the aluminum housing.   I will try to upload a picture.  Are there parts available to restore or convert this vent so it can be closed?