If you do some careful measurements, you might be able to find a match with one of the products here (also on eBay) :
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i was looking around there
to say the truht i havent mesured the dome my self yet
as its quiet an undertaking to get it down from where it is
but looking at the hikvision datasheet it says
178.3 (7")
it seams some dodgy in between size
i realize that there are a bunch of other relevant measurements
but if i cant match 1 size i wont 5 (height, diameter ...)