Canard à la presse is quite an ambitious project LGHT, and I hope you're able to pull it off.
I would think that your chances of finding a source for a pre-strangled Rouen duck is pretty nil so you're going to have to find a young adult and strangle it yourself. And, I think that the strangulation should occur no more than a few hours before preparation of the dish. One option would be to purchase a duckling today and raise it yourself. It might be mature enough for slaughter by Christmas.
If your successful in securing and slaughtering the duck, how do you intend to press it? If you're going full traditional on the dish, you'll need a proper presse and, if you can even find one, the cost will run into the $1,000s.
I've never had the dish but I saw it prepared several years ago at a nearby table at La Tour d'Argent in Paris, and the process is something to behold. The strangled, plucked, and eviscerated duck is briefly roasted and brought table side along with the presse. The breast is removed and sliced for serving, and legs are removed and returned to the kitchen for further cooking and returned as a second course. The remaining carcass is then put into the presse which is screwed down and then emits a small trickle of blood into warming vessel for the sauce. The sauce, if I recall correctly, is made up of Port or Madeira, smashed ducks liver, lots of butter, and, of course, the blood. Once complete, the sauce is spooned on the breast slices and the first course commences.
As a side note, every person who has the dish at the restaurant receives a small card with an etching and the number of the duck that was served. I don't know what the total stands at these days but it's in excess of 1 million as they've been preparing the dish since the early 1800s.
Best of luck.
