I looked at some smoke eaters of different brands and they are way outta our price range :/
Sounds like you are looking for a cheap fan setup, so...
Build a shelf in front of that opening or place to cut an opening.
Buy a cheap 20" box fan and screw it down on that shelf, tight to the opening.
Add a roller switch to the cord because you won't be able to reach the fan switch or plug the fan cord into a power strip with a switch.
If it seems to work for what you want, shop around for some kind of screened louvers to install over the outside opening.
I am guessing those louvers will be the most expensive part of the install.
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