I have a thru-wall pull chain exhaust fan in my kitchen. It was probably made by Nutone or Broan 35 years ago. The diameter is about 9 inches. When I pull the chain and the outer cover opens bugs can fly in, so I put in a round screen made for this purpose years ago. Now it is worn out and can’t be cleaned anymore. Where can I buy a new one? When I look on-line I can’t find what I need. When I ask in retail stores they look at me like I am crazy and want to sell me a new range hood. Can anyone tell me where to look? (I have available a photo of both the fan and the screen to clarify what I seek.). 10/31/06