Oh! And I don't remember if I told you, but I'm using a Don Post Boba helmet too. What I did was cut out that whole plastic visor piece and replaced it with the welder's visor.
If it's a fear of messing up the structure of the helmet, then I'm sure another Mando near you could help. If you can find someone that is. It's actually not too hard, but you do have to be careful.
If you do that, I know that there isn't much extra room for gluing the visor in, but it should be just enough. Just place the welder's visor in front of the helmet's visor and trace it with about half an inch extra room to glue.
I would also suggest getting some bondo to fill in the Don Post logo on the back and the dent. (Unless you want the dent) For extra weathering, I used the "magic sock". (Put some gray/silver paint on the sock while inside out and lightly brush it on the helmet.)