Bathroom extractor fan - backdraft excluder?

[MattM1]

We have a wall fan in our en-suite bathroom, with it being a small area it’s always cold & to top it off, near our property there is a recycling centre that dries / burns wood - as you can imagine the smell of smoke fills our bedroom. I believe there are draft excluders which can be placed within the thru wall extract duct to prevent backdraft - I assume this should also help reduce the smell?

Can anyone suggest a product?

 

[Burnerman]

I have an earlier version of one of these:

100mm 4" Axial Auto Shutter Fan with Pullcord

Wall, ceiling or window mounting

www.cef.co.uk

The back shutters work well enough and cut out noise and draughts. The shutters take about 30 sec to open though, being driven by the motor.
John