OOK 15 ft. 50 lb. Nylon Invisible Hanging Wire 50104 - The Home Depot
Working with Wire - SparkFun Learn
Hillman Invisible Cord 25 Feet 15 lbs in the Picture Hangers department at Lowes.com
PLCatis Clear 2 Core Cable 0.75mm² Round Flex Electrical Wire Invisible PVC Greater Bend Flexible Cable Identifiable Two Core Cable for Small Appliances LED Solar Lights Wall Lamps 5 Meters(L) : Amazon.co.uk:
PetSafe Boundary Wire for Electric Dog and Cat Containment Fences - Durable 16 Gauge and 20 Gauge Options - Available in 500 FT & 150 FT from the Parent Company of the INVISIBLE FENCE Brand 20 Gauge 500 feet