Whoa! Now, that's a heck of a camera! -
I forgot why you needed one.
The old one failed after a storm?
Since it's encased in a molded blob, I guess you'd want an identical mechanical replacement.
Shame, 'cause a standard glass reed switch could probably be stuck in there with a big gob of chewing gum! -

And if you found the brand that'd turn to stone in a few years, you'd have a permanent fix.
Truth is, I haven't lately been able to find any reeds around anywhere.
Used to be as common as dirt at Radio Shack, in their parts bins and in their home security area.
Linuxman seems to have had some luck finding such things.
Maybe a bit of internet searching...?
Who/where would I suggest? All the electronic part sellers like:
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Digi-Key Corporation
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Mouser Electronics
Oh, and it looks like a four-magnet wheel.
Not sure where in the gear train that's mounted, so it may be quite accurate.
However , if you need more counts between birds for Ku, taking a page out of Linuxman's book and changing the wheel is the next step.
So, consider any change to the magnets, and how to mount a replacement reed as a single problem.