Keeney Plumber's Spec 3.5-in Stainless Steel Rust Resistant Strainer with Lock Mount Included in the Kitchen Sink Strainers & Strainer Baskets department at Lowes.com
The Plumber's Choice 3-1/2 in. - 4 in. Heavy-Duty Kitchen Sink Stainless Steel Drain Assembly with Strainer Basket KOHLER Style Stopper ESS3157 - The Home Depot