Just been into my local Lidl store and found 'in the middle' a selection of wardrobe organisers, the type that velcro over the rail and drop down to give ''shelves', one with a 'shelf' of 30 cm and one about half that width for £2.99 each. We have used the smaller size in the wardrobe for socks and undies etc for years and have now bought the larger size as replacement that will hold folded t-shorts , towels etc as well. like the one on the left here: