I eventually thought of the Critter-Flag.
This contraption has an elastic band, cut to precisely the circumference of Vladimir's shell, with one inch extra in case he gets bigger. Russian Tortoises don't get very big, and Vlad is already about one inch away from his final size (He's Eight years old (Out of Seventy) in the pictures).
I used an 18" length of wire to create the main "Pole" of the flag, as well as to attach it to the elastic. The flag itself is made of three Stapled-Together 2 1/2" squares of the material that you find around store-bought bunches of flowers. I wrapped the last 1/2" of the stuff through the loop of wire at the top of the "Flagpole" and stapled the flag into place.
Vladimir walks with this flag on his back every day now and loves every minute of outdoor time we give him - while we can relax about having to watch him constantly as he walks. If we lose track of him now, we just look for the Critter-Flag!
I hope other reptile enthusiasts will be able to use this knowledge as well - You can scale this project to size for almost any creature you may have, including:
You name it! As long as the sharp ends of the wire are above the elastic and the band is not to tight, you can make a Critter-Flag for all of your furry (Or scaly) friends.