At one time, a long, long time ago, I had limited success with breaking long toothpicks in half and sticking 4 or 5 into the frosting of each cake, (thick, blunt side out), and individually wrapping each one with plastic wrap. Then packing them into a box full of Styrofoam peanuts and marking "fragile" over the entire box. Almost 2/3 made it intact. Good luck!
"Food is our common ground, a universal experience." - James Beard