I got a real nice looking one made by Canton Racing Products. Its aluminum and rectangular so it mounts very easily. I purchased mine through Unique Cobras in Gadsden AL, 256-546-3708. The hose from the radiator goes in/out of the bottom so it sucks the fluid back into the radiator. I mounted mine to the front of the passenger foot box.
http://www.cantonracingproducts.com/...tch_tanks.html
Mine is similar to product #80-210, but mine has a regular radiator cap on top so its easy to refill.