I know this is an old thread now....but for future reference
mine had an odd shaped almost box dome. If it's anything like that I never could find a replacement.
I did figure out though there's no need to replace with the same thing....at least in mine.
as long as long as the flange length and width covers the opening, most any of the domes you can find online would work. Many of those seem to be better too.... better plastic I mean
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