Since 11mm (.433) is close to 7/16" (.437) the inside dia. could be 7/16" although that size is not commonly available(@McMaster).To do away with any major machining just get the 5/8" bore sprocket and get a 7/16" to 5/8" bronze sleeve bearing (6381K465) and with a hacksaw cut away for the key. Don't know how much of the key will be engaged or if there would be a size mismatch.