I am impressed that you remembered your username and password after 8 years!
If you need it for one-time use, fashion a simple frame from scrap and attach plastic sheets on the sides, top, and bottom. Choose a still, dry, early morning to spray.
You are in UAQ. I don't know if inexpensive PVC sprinkler pipe is available there, but you may be able to make an inexpensive frame from sprinkler pipe with 3-way elbows in the corners. Attach thin sheets of plastic or tarps with tape. Hold it down at the base with rocks, bricks, or sandbags. Done right, you should be able to take it apart and use it again and again.
Perhaps you need something more sturdy or permanent.