You will need eggcrate modifiers in small spaces because light bouncing around will reduce the effect you are trying to create.
I use two Cheetah Boxes 24x24 and the eggcrate (soft, foldable) comes with the unit. Bigger boxes are available with eggcrate, too. Look at the Fotodiox units, availalbe from Amazon or directly. 24 can be too small for portraits that include more of the body.
Buy simple muslins and black cloth, too, for light control.