There is also a nice cigar store on the ground floor of Lagoona Mall. Its directly below Carrefour Market. They have a nice selection of cigars and cigar accessories.
I'm not a smoker but you may find the following useful! You can buy cigars at QDC, there is also a little shop outside carrefour in city centre that has a good selection. Failing that you could try the cigar bar at the Ritz etc... (any hotel with a cigar bar will stock them.)