The IcyDock MB994SP-4SB-1 is just such a unit - it packs (4) 2.5" HDD/SSD drives into the space of a single 5.25" drive bay and provides unified power and SATA hook ups at the rear. On top of its high density convenience, all four SATA drive bays are hot swappable without the need to pop off a side panel or disconnect cables.



Link: PCStats