Welcome to Basenotes!
I am far from being a Montale expert, but, as it is a Paris exclusive, you may just have to contact them and order it directly from Montale: http://www.montaleparfums.com/vpcA.htm
One of our members, maisonstinky sells Montale fragrances. I don't know if he is able to order BdA. If you PM him, please give him a few days (a week?) to respond - he has been traveling a lot lately.