Carpentry Question:Cedar Siding --- Replacement of a section of 7/8" thick cedar siding that is hard to find.

I need your help. I live in Gahanna, Ohio which is near Columbus, Ohio. I have a home that was built in 1994 with cedar siding, brick and concrete stucco. An area of the cedar siding needs to be replaced under a window where the cedar siding has deteriorated. The dimensions of the cedar siding are 7/8" thick, 8" overall width, with a 6" plus reveal. I can get away with replacing one board that is about 16' long. But; I can replace more if other deterioration is detected. I am worried that moisture is seeking its way through the deteriorated cedar to the building structure. I have caulked the bad areas to prevent moisture from entering the structure. The problem is, I can not find a vendor or lumber yard that can supply me with 7/8" thick cedar siding. Futhermore, the lumber yards and vendors are not much help in directing me to a supplier that can supply 7/8" thick cedar lap siding. I really need your advice and direction. Can you help me to find a supplier in Ohio?