Hope is not lost!
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.
Goodluck!