http://www.nikonchat.com/10-5mm-nikkor-fisheye/

Can I get a polarizer for a 10.5 DX Fisheye-Nikkor ED lens f / 2.8 G?
It is an exceptional lens, wide angle, which is what I need for the type of photography I'm doing. I can tell by the curve of the lens is not the type of lens having a polarizing filter or co … Regardless, I love the color saturation, so action is needed downward bias. There is no filter thread for this purpose. A lack of hitting one, anyone have any suggestions?
I do not know this, but some similar goals make filters in the back of the lens. This would not work very well for a polarizer, It would have to remove the lens to activate the filter. If you are using for the shots of sky, be aware that the polarization of the sky varies, so get a sky with one or more dark regions, not a uniform dark sky.
Nikon D90 Video Test with Nikkor 10.5mm fisheye