I'd print and paste, or buy from someplace like this. Alternatively, you could make your own rubber wheel-stamp with some creative carving, rolling on the ground and against another roller to ink it. Can I leave it as an exercise for the class? 
For ease of deployment, I'd much rather dead reckon between markings each X centimeters, of course, as suggested at the end of my post.
Depends on the requirements for accuracy and the capabilities of the dead reckoning.