Kenmore sewing machine replacement part

Question

My mother has a Kenmore sewing machine that was purchased in the late 1950's - early 1960's The model number is 566-1823 and the frame # is 3708. There is a small rubber wheel that is near the hand wheel on the side of the machine that is used in winding the bobbin. This rubber wheel has developed a flat spot and I am looking to obtain a replacement part that contains this rubber wheel. Any help you could provide in locating a replacement part would be most appreciated. Thanks.