What helmet did you buy and then not use? I use an outdated bicycle helmet with a brimmed hat underneath. The hat has slots cut for the helmet straps, and the helmet was selected from my collection as one where I could unthread the strap, thread the strap through the hat slots, and rethread the strap for the helmet. Most bicycle helmets have sewn straps which prevent adding the brimmed hat cleanly. I have met one other person doing summer hiking with a helmet. She also had knee pads and maybe other pads, possibly hockey, because as she said she frequently fell and wanted to minimize injury.