Where can I find Confit de Canard?
Go to Arrowine in North Arlington. I made a cassoulet over the holidays. They carry the duck leg confit most of the time and were able to special order the duck and armagnac sausage from D'Artagnan with only two or three days notice. Speak with Perry, who is the deli manager. Arrowine also carries a good but domestic garlic sausage.
I got duck fat and the veal/duck demi-glace from Balducci's in McLean, VA. Again, though, they are D'Artagnan products so Perry can most likely get them for you.
I suspect Dean & DeLuca will also carry these items; I didn't have too much luck with French ingredients at Whole Foods.
Good cooking and eating to you-
You can order direct from D'Artagnan off their webpage, they have everything you'd need I'd guess.
Are you looking for making it at home or as a dish in a restaurant? I'm not from DC, but Petit Louis in Baltimore has some of the best duck confit ever. Nasu Blanco also has a very good one.