Checking with Google -Fu search term:

metal H channel for panels

H channels are available from a few sources, but usually for large orders. A few "hits" below...

http://www.johnsonrollforming.com/di...N2/category/33

http://www.brunnerent.com/Tools/Port...0&lngDisplay=0

There are some in plastics (omit the word metal in above search) as well, which might work OK...

http://displayproductsonline.com/ext...annel-278.html

Have fun obsessing over all that. ;)