source for aluminum extrusions for foamboard displays?

[ztirffritz]

Have you tried McMaster Carr?
http://www.mcmaster.com/#aluminum/=1252vfk

Another thought is to try building with 80/20 pieces. It's like an erector set for adults. My company makes lots of stuff out of it because they can do it really quick and dirty.
https://8020.net/