Here is a slight variation. I ordered these little stainless steel cleats of “Wish” website. Super inexpensive (got 10 for about the same price as on SW-Motech. I fastened them with stainless steel 8-32 screws with a small rubber “O” ring to ensure a seal. The backing plates need to be made individually as the offset from the side of the lid is different on each cleat.
The bags are a double ended bike packing bag which is super weather proof and expandable for need with both ends rollable. The bag is attached using a river rafting strap (cam lock) which in my experience how’s much better over rough track than bungee cords.