The best thing about a Cultural Artifact in Public Speaking is that it can be just about anything! Literally. It can be a cell phone, a T-shirt, a stuffed animal, or a pair of sneakers. The most important characteristic of any Cultural Artifact is its unique significance to YOU.
In order to find your Cultural Artifact, simply stand in the middle of your bedroom/office/workspace, and turn slowly in a circle, allowing your eyes to pass over as many objects in the room as they can. If there is anything in the room that has emotional resonance with you, it should stand out to you at this time.
My Cultural Artifact turned out to be an old blanket, tucked in the corner of my closet.