Hi guys, I'm new here. I saw the post here and I thought you may be my Holy Graal of salvation

I have a few questions:
1)Where can I buy red window film and what's the best way to attach them to the lenses?
2)I saw gas mask come in different sizes (1,2,3,...). How can I understand which size I can buy?
Sorry if I repeated a question you already answered, but I'm not good with english