I can get really good artisanal chickens at The Local Butcher Shop in Berkeley. Our favorite preparation is the signature Zuni Cafe Chicken, which would be amendable to this modified technique.
Harder in to find great birds in New York City.
I've been twice to Yakitori Kono, and that's the best chicken I've ever had. He spent six months searching before contracting with a Pennsylvania farmer; here's a video of his operation:
How Chef Atsushi Kono Makes Chicken Skewers From Wings to Testicles — Smoke Point
Westermann clearly has a few gallons of stock simmering when he needs it. I sometimes do, but this is an ideal application of sous vide: Thaw one freezer packet of stock, and vacuum pack it with the bird, then cook in a water bath as indicated. The stock gets better, same effect on the bird as a bath in a huge stock pot.