if you are based in delhi...then go to nehru place and you will get a plethora of buying options....
but beware that most of the casings that you'll get will be a cheap chinese ones...with inferior metal casing and super inferior connecting panels....
both the IDE and SATA versions are available and it might cost you around 300-500INR average...
but IMO you should go for a better quality casing from either coolermaster (not easily available), vantec (you'll get this from SMC International) or even Transcend casings ( you'll have to ask around for this one)
these casings may cost you more ...but they will have proper ventilation, and a sturdiness about them..