If you have some basic woodworking tools and skill you can make something better than that for a fraction of the price.
If you don't have the tools or the ability, for the $99 price of the one in the link which is made of plastic
You could probably have one made for you out of birch or oak plywood at a small cabinet shop, which in my view would be substantially better than plastic.
Here are two examples of DIY mast style panel holders from WC:
If you use both stretched canvas and rigid panels you could make cross pieces that better fit the two different thicknesses, or have one edge fit the canvas stretchers and the other edge with a groove for panels, just rotate them as needed.