My flapper broke. I looked at ordering a replacement cover, but
, some were too small, others too big. I contacted Bigfoot
and they stated there is not an issue with putting a larger one on, essentially cutting the opening bigger if I so chose. The smaller ones would not cover the holes of the original. Did not want to cut a larger hole because I didn't think, and still don't, that the cut out would match the exhaust vent.
So, what I did is I took some fine mesh screen, patio door stuff, and I cut out a square a little larger than the size of the vent opening. Then I rolled it up and shoved it into the opening.
Then I took a piece of foam carpet padding, not the cheap rebond stuff that falls apart, and I cut a piece that I could stuff up in to block off the vent and easily remove as times warrant.
Works great, minimal expense, and no cutting into my unit.
I don't know if this will work for you, but if so, great!
will sell and ship you a new vent cover if you contact them.