Finished helmet fan installation with 9 volt battery and on/off switch.
Soldered wires together and coated connections with glue gun.
Battery can be replaced by removing top plastic cover again.
Came up with a new way to attach face mask to helmet rather than having an elastic band around my head which was too tight.
I riveted plastic tabs on the top of mask that insert inside helmet slots, and then use a short piece of elastic looped onto screws to hold mask in place.
This way the mask stays attached to helmet and slightly tilt to adorn helmet and mask in one piece.
This new way of attaching mask also allowed for the helmet fan to blow air onto eyes to reduce fogging up.