Any sailmaker/canvas/upholsterer should be able to help you out if you want something really custom.
Your pattern should work if you or someone you know is handy with a sewing machine. However using a quality material like Sunbrella is worthwhile, nothing else will last, and many home sewing machines will not handle the typical multiple layers of Sunbrella in the seams. Also it is difficult to find thread that will not break down in the UV, and thread used by the pros require special larger needles on the machines.
That said, you certainly could try to get the raw materials from a local canvas maker and take a shot at it using the patterns you have made.
Count on a couple of hundred dollars if you have one made, half that for materials alone.