Buy some large 100mm PP castors, plank of wood, screw a Really Useful Box of 9L (short narrow oblong) 18W (large fat oblong) 19L (tall narrow oblong), attach a vertical pole for manoeuvring, done. You may want braked castors if on a slope.
You can buy something similar, with drawers, but the weight can become a pain unless you have a sloped door threshold.