How about somebody posting a couple of pics of this critter. Especially showing the custom part of it.
It is certainly possible that it is proprietary, bearing companies will make whatever you want.
But the minimum order for something like that makes it very unlikely in this case.
Over the years, I have had to find some very weird stuff. I've gotten pretty good at it.
I downloaded the installation manual for the kit I think. It does not show a good picture of it, but it does refer to the "bearing with the raised inner race".
Whatever that means.
If I can get an idea of what we are looking for, I'll check around.
I know size is critical, but the main thing I need is what is different. If I can find who makes something like that, and what it is called, then maybe I can find one the right size.