PETG or light plexi with window tint is better for visibility. A welding visor is really dark.
When I was in AZ I went by the local auto tint place. They gave me some scrapes free of charge. Depending on the state you may be able to find mirrored tint. This is usually for buildings. Limo tint can be purchased at auto parts stores and welding visor replacements can be found at Lowe’s Home Depot or harbor freight.
The thing I like about PETG is her can be cut easily, (lots of scoring passed) heated and shaped with out distortion. If you go this route make sure you apply soapy water a teaspoon in 32oz of water should do.
Then squeegee out the water and give it about 1/2 he to dry and you’re golden.
Cut just a little bigger than what you think you will need. You can always trim it down.
You can also make a template with masking tape.
Cover the inside of the visor area with two layers one vertical and one horizontal. Mark with a sharpie. Then peal off. Lay flat on what you are cutting straighten lines with a ruler and score with tape in place. Keep in mind that you will want to apply template to the back side of the visor this will be the inside of the helmet.
Hope this helped good luck. 🍀