Nikon 16-35, Polarazer and ND Grad filter

I need your help. Tried to use Nikon Polarizer (old model) on 16-35mm lens and have vigneting at 16mm. Could not use ND Grad at all because thread outside on Polarizer is not 77mm.
Using 77mm ring and Kokin filter holder without Polarizer also gives vigneting.

So the question is: Which polarizer, ND grad, and filter holder should I buy to avoid vigneting.

Thanks a lot