You can buy the fabric and install it yourself. When you order it, you'll need to tell the person you order it from it's a 21' patio awning.
The Reader's Digest version of the installation instructions are:
Take loose the rear rafter arm, and unwind the arm. It has a spring with lots of tension, be very careful. Drill out the rivets holding the old fabric to the roller tube, unscrew the center cover slat, and slide th old fabric off the tube. Installation is the reverse of removal, and the spring gets wound one turn per foot of awning.