Danco 4-Pack Standard Aerator in the Faucet Aerators department at Lowes.com
12 Pieces Faucet Aerator Replacement for Sink Aerators and 5 Pieces Faucet Aerator Key Wrenches Removal Tool M 16.5 mm 18.5 mm 21.5 mm 24 mm Tap Aerators Flow Restrictor for Bathroom Kitchen - Amazon.com
Replacement Tap Aerator Plastic Water Saving Insert 16-24mm for Kitchen Bathroom | eBay