just go to a computer store and look at their 2.5" external enclosures... I got a nice one for like $25. Because the drives are so small, the enclosures are small too.
OWC www.macsales.com sells cases for 2.5" laptop hard drives. It is completely bus powered so no external power supply is needed. I buy from them all the time. Great service and support. Give them a call.