Any non-SATA external case (which is to say nearly all external drive cases) should work fine with that drive, although if you don't have USB2 on your Mac, you'll want to be sure to get one that has a FireWire port, or it will be REALLY slow transferring files.
Don't get it from Staples or the like--they mostly only carry ones that already have a drive installed, and are probably drastically overpriced unless on a big sale.
If you don't have a favorite online seller of this sort of thing (I usually use NewEgg or maybe OWC), just go to DealMac.com, go to the storage section, and pick out a decent-looking 3.5" one (either USB2 or dual USB/FireWire), and get that. Probably will cost around $25 for USB2 only, maybe $35 for FW.