... You will get a fight from the Neighborhood Association. (This is a perfect example of why I hate them! Here, you want a long-lasting, cedar-looking roof, and if you do what you want to do, you'll "bring down the value of the other homes in the neighborhood.")
They make what you want but I believe it's an asphalt-based product. I'm not sure how 'broad' a definition you use when you say synthetic. Look in the Yellow Pages under Roofing Materials & Supplies and Roofing Materials for Retailers in your area. Home Depot may have them but they may not be a stock item. Just go to the BUilding Materials desk for help.