Massive bags, similar to a builders bag but twice the height and with a (sealed) opening at the bottom.
You can fold the top down and make the sides double thickness for an extra sturdy bag of you don't need the height. Alternatively they'd provide big section of sturdy fabric if cut up.
1 taken but 2 still left
2x double height builders-type bags (Corsham)
This offer has been gifted to someone and is no longer available.