For the money, it's hard to beat regular old heavy duty aluminum foil. For years, I used a long sheet folded over several times as a nice compact, lightweight, durable, and effective windscreen for my little Trangia alcohol stove. Then I found regular small sheets of aluminum flashing. That makes an even better windscreen. Curve it to the shape you want, slightly tighter actually, and it will spring tightly around the base of whatever pot/burner combo you're using.