Hi Phil,

You won't find the extrusion cut to length. They will cut it for you though.

This is what I bought:

Qty 2 - 20x20 4H Light Plain profile cut at 2000mm.
Qty 2 - 20x40 6H Light Plain profile cut at 2550mm. I then cut it to 500mm lengths myself. Dad has a suitable saw.
Qty 60 - 1.31.HM5 Maytec threaded plate.

This is who I bought it from: http://www.maytec.com.au/

You could also get the equivalent here: http://www.8020.com.au/

This is the mob that laser cut my acrylic pieces: http://www.citywestplastics.com.au/

Now you should be able to easily find the equivalent products in the US. I think 8020 is a US company.

Good luck!

Cheers
Jason.