Homemade pail panniers. I make them from plastic exMayonaise and pickle buckets that restuarant often throw away or charge $5 for. It takes me about 10-30 minutes to make them.
The one below I painted bright orange,wrapped reflective tape around, added a bike reflector to the back and left the bail on as they can be carryed more easily with your gear inside, also make great water carrying, seats and tables.
Fully made I will sell them for $40+. You can specify the color and anything else that you want done to them. The rack brackets are made to be wrapped onto the rack with bungie cords.
I also use them to arry home grocerys especially the bread to keep it from being squashed.