This doesn’t need to be complicated. On one cross-country trip, my friend and I took a small stuffed goat. Over the course of 3000 miles we told many stupid stories about that goat and photographed him with us in places ranging from the Hoover Dam to the Amish Country of Pennsylvania. A family member recently took a small stuffed Sponge Bob on her trip cross-country.
It’s not what the mascot is that counts. It’s that you have one. It will be the glue that holds the trip together.