Walaikumasalam..
Based on your query it is simple. Get your self fabric arranged and have TOP COVER tailored as per your needs.
Suggesstion :- Top fabric can be poly lining or any water reppellent fabric with the under ligning of any cotton soft fabric, as top layer will be hard and stiff. so the underlinging is important.
Through this you'll be able to have something which will save from rain as well as dust.
This is only prevention not 100% solution...