All SSD you will ever care about are 2.5". Just go buy whatever capacity Samsung 840 Pro drive you want. amazon.com or your favorite retailer. E.g.
http://www.amazon.com/Samsung-Electr.../dp/B009NB8WRU
Many people are using SSD for Pro Tools storage and/or boot drives. You can read the many threads on DUC about this. About a year or so ago Avid just approved/recommended any SSD drive as suitable storage. That was maybe being braver than I would be, but I really see no reason to buy spinning disk for use today except archiving/backup or things like huge video RAID boxes.
If you are on a Mac do not use a USB2 caddy, USB3 maybe or FW800 with an Oxford Chipset or thunderbolt. Or buy a drive already packaged e.g. From Lacie.
Darryl