Life as December Goat: Day 5 (Harley Question)

tnhillbillygal posted a pic said
7

Okay, I am using today’s opportunity to ask what this part on my husband’s Harley is called. We bought it recently and it came with this Willy G on it. We aren’t skull people and I’d like to get him a replacement for Christmas. I thought it was a gas cap but that is not it. Any help?enter image description here