The original poster of the security helmet said he bought a motorcycle helmet visor, I assume he cut it down. However I've searched numerous websites and visors and have been unable to find one with a color even remotely similar
My master chief visor was originally very similar to that. I.e. rounded and not flat.
So! Online may not be the best way, and depending where you're located you may need to travel a bit, but if you can find a motorcycle or motocross store, they will usually (not always, be careful) have a selection of visors. Be prepared to spend a little coin, though; mine came to something like $60 give or take, it was stupid.
You should be able to find one in a place like that.
Bubble shield visor I buy these for my motorcycle helmet *edit - like Loner161 mentioned ;D
I believed it was a bubble shield but after a lot of close examination, cross referencing side photos with different visors, I have noted that bubble shield is a bit too... bubbley? I believe the visor he bought is remarkably similar to this one in shape Icon Variant Motorcycle Helmet Visor - Gold Iridium | eBay, but the color is off by a long shot.
Update: I see now that the visor is definitely cut down (I suspected this for awhile) due to the small amount of chipping around the bottom. I can also assume that its not fully mirrored due to it having an almost gradient effect from the top of the visor, where more light would be hitting it, and the bottom, where you can see the back of the helmet, the wood its sitting on, and the wall behind it. I am also assuming its not actually a gold visor and most likely is a bronze, pilot helmet style, motorcycle helmet visor due to its very unique shape. It doesn't bulge out far enough to be a bubble shield, tho that was my first guess.
Ill be heading to a store in my local area that sells motorcycle helmets and visors in a small hope that they have this specific one, or one of a similar shape and color.