I totally have to do that to my welding helmet also. No more draping a trouble light over one shoulder or welding at a crappy angle just to get some light at the right spot.
Found this at Princess Auto on sale for $2.49, LED, takes 3 AAAs, is adjustable up and down:
View attachment 224770
I'll cut off the straps and get a small bolt to hold it to the helmet. With a single bolt, I'll also be able to rotate the light sideways if necessary.