I purchased the part from newr3.com in the summer of 2010. Don't know where they got it, or if it was drop shipped.
I don't have the old brackets anymore. Tossed them after I made the templates. I meant to run a magnet by them to see if they were aluminum, but never did. I assumed they were aluminum by how flexible they were. Either way, the ones I had look like the ones in the picture and they were too week for the job. There are different grades and thicknesses of stainless.
If this sounds like your product, I would like to take you up on the new brackets. Though my home made ones made from 'L' bracket that I used to hang my garage door are pretty strong. I don't notice any movement at all. With the stock ones, I would notice movement when I wiped it down. Which is about once or twice a year.
Other than the brackets, it's an awesome product. the finish is still smooth and it handled the scraping on the ground well. Just a few scratches. No major gouging.