Nylon washers in Euro-reef Sedra needle-wheel pump impellars

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My Euro-Reef is 4 or 5 years old, I forget which.

There are 2 nylon washers that rub against each other and they have worn concentric donut-type rings in each other.

Is this a generic off-the-shelf part that can be bought somewhere (I don't have a big box hardware store in my town or I would look myself). Or is this a specialty part that has to be ordered from Euro-Reef only?