Have you looked into renting a bending brake?
Another option is a homemade bending brake. I can't find the web page I used for building mine, but I had good luck with bending up to 0.050" thick aluminum up to 48" wide up to about 140 degrees. There are a number of articles out there on how to build one yourself, using hinges, steel angle (and/or wood), and clamps or bolt/nut sets. It wasn't too hard or expensive to build - probably about three hours work and less than $100 for everything - nor was it hard to learn how to use.
I found the article - but not the original website. See
http://www.cannedhamtrailers.com/pdfs/davesbrakeplans.pdf for the article that I used as the basis of my build. I went with smaller sized steel angle since I was only going up to 48" long, rather than the 96" the author used.