Walmart offers this Duck Brand Heavy-Duty Weatherstrip Seal for Large Gaps 2-Pack for $4.84. (Amazon charges the same with orders of $25 or more.) Opt for in-store pickup to avoid the $5.99 shipping charge. That's $4 off and the lowest price we could find. Each roll measures 3/8" x 1/4" x 17-feet. It's designed to seal the perimeter of outside doors.