Obviously, at the end of the day you can do whatever you want with your costume. Now, if it were me, I wouldn't.
The Visor you linked to on Etsy is not opaque, or mirrored. In the picture you can still the features of the display head they have it on. It is very likely that if you put that in your helmet, people would be able to see your face/eyes behind it. One of the defining features of the SPARTAN helmets in Halo is their visors are a solid color, non illuminated, and usually mirrored, or at least very reflective, color. The Hayabusa helmet was only featured in Halo 3, where it had a gold visor.
If you are making the visor the curved flat peice like it is ingame, with no crazy detail, you can get some plexiglas glass and heat gun it into a curve. Then put some friction fit one way gold window tint!
This recon helmet I helped my friend build. I did the vidor exactly what I recommended.
I plan to redo my helmet visor, which is bent more into a trapazoid shape... like this: \_/ did the same thing. I want to add a hexagon effect aswell, so I will be receiving a hexagon hole puncher from jo Ann fabrics soon to hole punch painters tape. I will then put the tape on the plexiglas glass and spray paint with a slightly darker green, peel the tape off, then apply the tint so it shows through
Excuse how wrinkly it is. This was my first attempt at using tint. I didn't use enough water