Have you confirmed that the reservoir fits on to the MC correctly? The aftermarket equivalent of the 46660 SE0 013 part number is available from Rock Auto and a bunch of other suppliers. It cross lists to a lot of of Honda products; but, not the NSX. I know that the large cap on the NSX reservoir has a common diameter & thread (but is not identical) to a lot of older Honda products because I pulled one from an Accord (I think - fuzzy memory) in a salvage yard to make an adapter to pressure bleed my brake system.
So be cautious. It may look like it should fit; but, may have fit 'issues'.