Electrolux -- as well as many other vacuum cleaner companies -- did offer storage hassocks as an optional accessory. I believe they were first offered cir. 1949-50 and as late as the Model G. Thereafter, they disappeared. I remember many a little old lady who had an XXX, LX, E, F, R or G and stored it in their hassock!
Companies I know of who sold them, in one form or another, include Compact, Electrolux, Filter Queen, Lewyt, Eureka and Apex; and probably others as well.
Also, you could buy a hassock at many vac shops.