This is Compta38 on Youtube, but I'm sure you know this
heres an answer I copypasted from my channel.
Hiya Queen
On your helmet you have like a hole there for the tubes right? On the one I built I just cut some pipe from home depot in half and hot glued them in. For your helmet you might have to fiberglass in a place to glue your piping into. Or find some flat plastic to glue in around the area to cover the holes then glue in your pipe. The pipe is sold by the foot in Home Depot on the large spools.
On the visor what I did was wrap the visor itself in blue painters tape and velcro it inside the helmet in its place Then I sprayed Great Stuff expanding foam into the gap. You'll have to do some trimming to the great stuff after it dries, but thats easy. Then you just bondo over the great stuff, and sand it down.