I've had 3 vans with roll out Fiammas or whatever the similar things are called. They are a pain. Ah yes, Omnistor.
I bought a canopy from Temu which works well, didn't cost a lot. It attaches to the roof rails with two velcro strips that wrap round the roof rails. I added a third in the middle. The poles weren't very robust so when they bent as soon as the dogs wrapped their tie out leads around them, I swapped them for a couple I had hanging around at home from a gazebo type thing I've had for years. It isn't 3m x 3m, but then the roof rails on my little van aren't very long. I guess with longer rails you could make up your own easily enough with a tarp, some guys, a couple of poles, and sew on some velcro tie wraps. If you search for "car canopy" on Temu you will see a few different ones, they do come in bigger sizes than mine.
