where can i buy the dvd?

You won´t be able to get the DVD anywhere because it was never released. Whenever you wish to know if a DVD has been released, you check the ¨DVD details¨ on the imdb vertical menu on the left of the imdb page.
The best you can do is read the novel. Amazon sells it but I am sure you can get it everywhere else.
http://www.amazon.com/exec/obidos/tg/detail/-/2221047915/103-0361733-9 235072?v=glance
Have you seen the film ¨Ararat¨? It´s out on DVD according to imdb and it´s about the Armenian Genocide as well.
You can also get a hold of documentaries on the Armenian Genocide.
Check this out:
Armenia, The Betrayed and Armenia, The Massacre: http://www.ourararat.com/eng/e_video.htm
Hope this helps.

I too want to see this excellent film. I have seen it sold through Amazon - France but I do not know if it has subtitles in English.

In Netflix is called "588 Rue Paradis". Thats how I saw it. Beautiful movie.