I use the 3M wiring marker tape in the little red dispenser that costs almost $50 (go figure)local electrical supply will have them too, probably cheaper too

Amazon.com: 3M ScotchCode Wire Marker Tape Dispenser w/ Tape STD-0-9, Includes 1 each of 0-9 numbered rolls : Office Products
Amazon.com: 3M ScotchCode Wire Marker Tape Dispenser w/ Tape STD-0-9, Includes 1 each of 0-9 numbered rolls : Office Products
www.amazon.com
It's handy but, I would never pay that much for one. I've had mine for so long I don't remember what it cost.