Amazon has the Carlisle Flo-Pack Commercial Grout Brushes in $1.08 with free shipping for Amazon Prime or orders over $25.
Product Features:
- Remove mold and mildew buildup on tiles.
- Durable nylon bristles.
- BPA-free.
- Bristle area measures 2.75-inches long, and the overall brush dimensions are 8-1/8 x 1 inches (L x W).