No suggestion on homemade blinds but i do have one for your pop ups.
Buy one of those adjustable aluminum tent poles. Take the blunt end and make it even wider by wrapping a towel all around it and over the top creating "soft ball" and secure it with duct tape
Then each time you leave the blind, prop that end up against the center of the roof hub and the other end in the dirt. This will help keepthe roof up until you return next time.
I had my first one break also because ice and snow collapsed mine then just kept building on it until it snapped