Vixit (France decor). Chocolat-Chocolat might have it (I am sure they have a pistachio praline). Possibly Ares. I think I have seen it at the vrac de marche at some point long ago, but it might be a seasonal item that they don't have now. I would call and ask.
Edit: Yes, Chocolat choclat has it. The question is, how much do you need?
Chocolats Privilège at Marché Jean-Talon. At the store they just have a small 40 gr. format, but you can ask them for bigger size and they will prepare it for you.
You could probably ask to any pastry shop using pistachios in their desserts too. I bought some from Rhubarbe one day.