After watching some YouTube videos and reading forum searches, I got a few ideas to install a small cooling fan inside of the helmet.
Found a perfect mini-fan and 9volt battery connectors at Radio Shack.
The helmet I used originally came with a on/off switch, that still works and would fit on back of helmet.
I drilled vent holes on top of helmet ridge cap for air intake, and a hole below the fan for airflow into helmet.
During installing of switch, I had to re-glue a plastic piece that came separated.