You can get a big one for cheap from China. You'll want to waterproof it, since it's just canvas, but... It's cheap. Your husband knows how to get a hold of me if you want more info.

Here the covers are something plastic I guess, not canvas🤔 Or it looks like fabric of some sort, but is heavily covered with some rubber. What I saw was a yurt with isolation and outer and inner layer, I'm not sure canvas would survive the winter🤔