Amazon has the 300-Feet Irwin Tools Strait-Line Flagging Tape (Red; ‎GIDS-286255) on sale for $1.69 with free shipping on $25+ or with Prime (extra 5% off for 5+ S&S orders). 

Made from weatherproof PVC. Used for construction, landscaping, excavating, identification of trees or hazards and locating underground cables or pipe.