You'll probably hear lots of references to Zip-Dee Awnings (made outside Chicago) which are the single most common on Airstreams. They use durable canvas material in solids or blue/white stripes, and have long track record of fitting curved side arms and attachments designed specifically for Airstream trailers.
Their web site is http://www.zipdeeinc.com/Index.html
I suspect they're not the least expensive alternative, and that honor probably goes to "Carefree of Colorado" vrand, or potentially A&E. They use vinyl fabric, often in horizontal patterns, and I'm not sure they handle curved sides of Airstreams as effectively as Zip-Dee does. Zip-Dee also generally provide metal housing sections for retracted awning, which help a lot to protect fabric when awning stowed in Calif sun or winter rains...
We have Z-D on ours, and fabric pretty durable, structure pretty solid (spring-tensioned bars and locking braces..) and are pretty happy with it. They can refer you to local dealer from web site, or independent shops may be able to install if you have unit shipped from factory.
Camping World and others sell Carefree or A&E lines, and I'd have a LOONG talk with them about fitting to your trailer before ordering anything or committing to an installation appointment... (They reneged on published install quotes and refused to install Fantastic Fans in our trailer, due to curvature of roof...)