3.5" removable SATA hard drive bay - 3.5 inch mobile rack SATA mobile rack with no need for a caddy - YouTube
2.5" Drives in 3.5" Drive Bays - drive adapter options
StarTech.com USB 3.0 / eSATA Dual-Bay Trayless 3.5" SATA III Hard Drive Enclosure with UASP - 2-Bay SATA 6 Gbps Hot-Swap HDD Enclosure - Connect two hot-swappable 3.5" SATA III hard drives
Single Bay 2.5”/3.5” HDD Cage for COSMOS C700 Series | Cooler Master
Amazon.co.jp: StarTech.com 3.5" Bay Hard Drive Case, 2.5" Hard Disk Detachable Mount for SATA/SAS Compatible SSD/HDD Convert 2.5" Drive to 3.5" 25SATSAS35HD : Computers
ORICO 5.25'' Inch PC Drive Bay 3.5'' SATA lll HDD Hard Drive Internal Caddy Case | eBay
5 Bay 2.5" and 3.5" SATA HDD External USB 3.0 / eSATA RAID Hard Drive Enclosure
ORICO 3.5 inch 5.25 Bay Stainless Internal Hard Drive Mounting Bracket Adapter
Akasa 3.5" Device/SSD/HDD Adapter | 5.25" to 3.5" Bay Adapter | 2.5/3.5 Inch Hard Drive Enclosure | SSD Mounting Bracket | For 5.25 inch PC front Bay | AK-HDA-05 : Amazon.co.uk: Everything Else