Hi, I'm renovating my grandparents house that was built in the 1930's. The kitchen sink was made by the Standard Sanitation Company, they became American Standard, I believe that the sink is enamel on cast iron. Each basin is deep but it's not a deep fireclay or farm house sink. One of the drain openings is 5 inches. I have found some 4.5 inch strainers but no 5's, even for commercial sinks. Has anyone ever had to find an odd sized strainer & basket?

I don't want to replace the sink because the tile on the counter & backsplash are all original so I would never be able to replace it if was damaged. Could this sink be a one off? Could I use the 4.5 strainer & have a sleeve or flang fabricated to sit it in? Thanks for any help & advise.