Find out if a film is on iTunes, Amazon Prime, Netflix or Now TV

Searching for Kang-ho Song

Is Memories of Murder available on iTunes, Amazon Prime, Netflix or Now TV?
Is Snowpiercer available on iTunes, Amazon Prime, Netflix or Now TV?
Is Sympathy for Mr. Vengeance available on iTunes, Amazon Prime, Netflix or Now TV?
Is The Good the Bad the Weird available on iTunes, Amazon Prime, Netflix or Now TV?