try to get some in india before you travel - try banks/exchanges...etc - since i'm not indian i cannot advise further - but i chose to reply just to inform you that airports in canada have the worst exchange rate (probably the worst in the world) its a ripoff. Although my experience was only with Toronto pearson airport (but i believe money exchanges in other airports in canada also adopt the same practice as they are probably branches of the same exchange office)
I got only around 83 CAD in exchange for a 100 USD!! While the bank's rate inside the city (Toronto) was 1 CAD for 1 USD at the time...but ofcourse i had to get some canadian dollars at the airport least to pay the airport taxi.