NDS 4 in Round Drainage Grates for Pipes and Fittings 1-1/2-in L x 4-1/2-in W x 3-in or 4-in dia Grate in the Outdoor Drainage Accessories department at Lowes.com
Black Square 12" (305mm) Cast Iron Heavy Duty Gully Grid Drain Cover Grate Metal | eBay
Rain Bird DG12SFB - 12 inch Plastic Square Flat Drainage Grate - Black