Our club uses Surveyors tape. Its thin plastic, comes in a variety of fluorescent colors(our lastest batch is pink) that shows up well in both clear sky and clouds.We've used orange in the past- that shows up well too.
We found it at Menards on sale for 85 cents for a 600 foot x one inch foot roll. In these cold temps(20*) in the midwest, however, it does shred away at higher speeds.

I've also seen it in Walmart and Tru-Value hardwares stores too.

Swede