Walmart offers the Duck 100-Foot All Weather Repair Tape for $2.89. Opt for in-store pickup to dodge the $5.99 shipping charge. (Amazon charges the same with free shipping via Subscribe & Save.) That's $4 off and the lowest price we could find.
Update: Walmart now has a minimum purchase requirement of two per order; however, Amazon still offers it for $2.89 with free shipping via Subscribe & Save.