I've seen blacksmiths that have built similar deals and think that I remember seeing one on a post quite a while back. They are quite simple just a ridged frame to clamp the porta-band to. I think that the first one I saw just used a large hose clamp to hold the saw to the frame.
I had a friend here in town who purchased one of those for his dewalt saw....he brought it to my shop, in hope of making it more study. We welded a couple of supports on it, trying to make it stouter....but within a week he was back asking if I could build a stand for him.
For the price they want for that stand, I personally think it's a rip-off. The only thing that holds the saw to it are the table screws, and it flexes all over the place.
Here's some pics of the stand that I built for mine. The Dewalt saw is pretty easy to build a stand for....