I've purchased "Drive Shells" with USB for less than that at Comp-USA (I'm thinking 25 bucks)
You can also get shells already filled, however beware.
I have 3 USB externals
1: Adcom 160 Gig, This was my first USB external drive, It failed the "Bounce test" so I had to replace the drive, I bought a Western Digital 120Gig which simply did not work well in the case (Win-98 would see it, win-xp would not, however 98 would not install it)
I finally had to replace the 120Gig drive in the shell with another 160, both Hitachi (which is not installed permentally in my main computer) and Seagate (OEM) worked fine
2: Western Digital 80 gig, no comment, original drive in shell, works as advertised
3: The WD-120 is now installed in a low-cost shell from Comp-Useless. The only problem I had with this instalation was HEAT, the drive (and shell) got very very warm. A small (About 1-1.5 inch) wisper fan and a few holes in the shell (Fan installed near the back, holes in the front) and you can now store data and cool your drink at the same time (used to keep the coffee warm, Ok, Ok, it's not that cold or hot but you get the picture)
Installing the drive in the shell was simplicity in itself
Step one, open shell
Step two plug in drive (note cable select generally not a good idea, jumper drive as single master or dual master read instructions here)
Step 3, bolt drive into shell
Step 4: close shell
Step 5,6,7: Plug in power up and use
Tool needed, Phillips head screwdriver (note tool, not tools)
That's all there is to it, comes with screws