Lowe’s has 11.7-in Square Concrete Patio Stone, Grey for $1 w/ Free Store Pickup.
Notes: selection varies by store/region
- click on this link – go up one sub-category: Outdoors >> Pavers & Retaining Walls >> Stones & Pavers >> Pavers & Stepping Stones
dimensions: (Common: 12-in x; Actual: 11.7-in x 11.7-in)