I found this nice modular construction system for workplaces in factories based around 28 mm tubing. That could work well for mounting the solar panels. I don't know the manufacturer, but I found it for sale here and here. I ordered some components for testing. I rendered the construction that seems to be the most promising and used the images for the project thumbnails. I hope everything works out well when the parts arrive.

(Edit in 2024 - TechXXL never responded to my request and the order and delivery process with Maunsystem was very lengthy and riddled with communication problems, so I can't recommend either at this point)