I will echo the sentiments of contact lenses. If you can't wear them/afford there might be another way. I know a few guys in the 501st who have gotten lens from their old pairs of glasses and put them in, right behind the tinted lenses in the stormtrooper buckets (helmets). Maybe you could see if you have an old pair of glasses that you can pop the lenses out of, and mount those inside your helmet.