You should probably go to a store and look at some. Any of the plastic enclosures that appear to be in two pieces so you can wedge a screw driver or coin in between the halves and crack it open will be simple.
I did it with a drive from Pretec, but not sure if they make it anymore (I've had this one a long time before I decided to do it. Pics attached (before and after).
Original drive case:
Removed from case:
Installed in new case (the rest of the fake thumb I used is the cap, but it doesn't fit right, so no pics right now):