For in-store pickup, Home Depot offers the Performix Plasti Dip Rubber Coating Aerosol 11-oz. Spray Can in Black, model no. 11203, for $5.98. (Lowe's charges the same.) That's the lowest price we could find by $6, outside of the mention below. It provides up to five square feet of coverage and purports to dry in as few as 30 minutes.

A close price: Amazon charges $6.58 with free shipping for Prime members after clipping the $2 off coupon on the product page.