I did a Boba helmet a couple of years ago and used a safety face sheild from Lowe's. It was pretty thick and not very easy to cut with a rotary tool. It was easy to apply tint to it, which I applied to both sides, but ended up taking off the inside tint above the 'eyeline'. Fairly easy to see out of, but you can't see in it for poop. The visor fit alright into the helmet, but it was a '97 and didn't fit 'perfectly'. I installed it by drilling holes through the visor on the edges and screwed them into the helmet. I also used some glue to make sure the screws held.
I took that visor out and am planning to put it into my 96 Jango. I'll have no trouble installing it since this helmet is formed much much better. My plan to install it is the same, but to use countersink screws through the front and nuts inside. Once it's attached, I will putty up the screws and sand and paint them. I know that sounds a bit tough, but I've already drilled out the 3 holes in the right ear and the line in the left ear and all the 'divets' on the back of the helmet.