It is possible to use a generic lens hood which has a ø77 screw on ring on with a bayonet type lens hood that fixes onto that ring (reversible); I have a JJC reversible lens hood for my 35mm on the 645N. It is a matter of precision, as I look through the viewfinder, if the long extensions are horizontal, there's no vignetting, if slightly diagonal then there is. See
digitalmediastore: 77mm Reversible Screw-in Lens Hood
Unfortunately my scanner has been in storage for many many months now, and my dark room still awaits transportation, so I have no way to check this on the actual film results (the viewfinder not being 100% it is no absolute guarantee).
The triangular cut-outs help with removing vignetting from the corners, if aligned correctly.