Looking for non-standard extrusion profiles

[sunworksco]

Where can I purchase non-standard 6061 alumunim extrusion profiles?
I'm looking for something that resembles a 2" square tucked inside a 3" angle.I'm building a lightweight chassis and need this extrusion to fasten aluminum sheet for wall and floor.Similar to this image but with another flange creating an 90 degree angle

[rowbare]

Would this work? http://www.8020.net/Quick-Frame-1.asp

Edit: Oops you are looking for something bigger...