Amazon has 1.88" x 20yd Scotch Duct Tape (Violet Purple, 920-PPL-C) on sale for $2.66. Shipping is free w/ Amazon Prime or on $35+
Amazon also has 1.88" x 20yd Scotch Duct Tape (Sunshine Yellow, 920-YLW-C) on sale for $2.66. Shipping is free w/ Amazon Prime or on $35+ (Thanks AbedO)