So Keefer, do you want it? I'm replacing it with one that's 6" long so it won't stick up above the cover board and poke up into the trunk mat. I found what I need at a local hardware store and going to pick it up tomorrow and I could grab one for you too if you prefer one that length.
Regular carriage bolts have a smaller head than what originals do. I think mine is a 3/8 bolt, and I know the head is wider. They will work, but think it could pull through if overtightened.