ICY DOCK maufactures a wide range of 2.5" to 3.5" and 3.5" to 5.25" Drive Bay Conversion Kits that allow you to mount smaller SSDs and HDs in larger drive bays.
EZ-Fit Pro dual 2.5 to 3.5inch hdd bracket upto 9.5mm hdd, metal
EZ-Fit Lite dual 2.5 to 3.5inch hdd bracket upto 9.5mm hdd, plastic
Flex-Fit dual 2.5 hdd upto 9.5mm and 1x3.5inch to 5.25inch bracket, plastic
EZConvert 2.5 to 3.5inch SATA hdd upto 9.5mm, plastic, fully enclosed, hinged top
EZConvert 2.5 to 3.5inch SATA hdd upto 9.5mm, plastic, fully enclosed
EZConvert Lite 2.5 to 3.5inch SATA/SAS hdd upto 15mm, plastic, open frame
EZConvert Pro 2.5 to 3.5inch SATA hdd upto 15mm, metal, fully enclosed