Hallo Abhishek,

LM336 and LM329 are widely used.
If you want to have some maximum specification of long term drift list of suited devices becomes very short. Analog devices has some good (and expensive!) parts. Also Maxim has some good ones.

There's another way: There are some ADCs arround, having built-in voltage reference, which you can also use for other tasks. Only some buffering is needed. Advantage is, that precision of voltage reference is matched to actual need of ADC, mostly.

Bye,
Kai