There are (at least) 3 companies that make RV awnings. Carefree, Dometic and Solera which all have websites where you can browse what's available. Their websites should also list local dealers where you can buy one and have it installed. A dealer will also be able to size it for you properly so that it mounts in the same location as the old one. If you're planning on installing it yourself, there are also on line sites where you can order them.
2011 Chevy Silverado Crew Cab 4X4
2009 210 WBS