I would look into Bosch Rexroth aluminum extrusion (Metric version of 80/20), I believe they make some 20x60mm extrusion, and I was able to get some here in Canada, which makes me believe you might be able to find it in the US.
Why did you choose an Invision unit over an AlumnaFeed? Or even a Deltaweld? I know very little about those machines, but I would really like your opinion.
Thanks