Lowes has 8-in L x 4-in W x 2-in H Rectangle Red/Charcoal Concrete Paver for $0.25
https://www.lowes.com/pd/Holland-Re...-8-in-x-4-in-Actual-7-75-in-x-3-88-in/3010214
also gray
https://www.lowes.com/pd/Holland-Gr...on-4-in-x-8-in-Actual-3-8-in-x-7-7-in/3018456
ends Apr 10
https://www.lowes.com/pd/Holland-Re...-8-in-x-4-in-Actual-7-75-in-x-3-88-in/3010214
also gray
https://www.lowes.com/pd/Holland-Gr...on-4-in-x-8-in-Actual-3-8-in-x-7-7-in/3018456
ends Apr 10