Where do I buy chilhualces chiles?
Normally, I wouldn't post to say "forget it" but in this case, it would take a not-so-minor miracle to find them locally. They're hard to find nationally, and and for that matter, apparently fairly rare even in Mexico. Expect them to be a lot more expensive than the common varieties, but this place has them listed: http://www.thechileguy.com/products.htm . Fwiw, I did place a large order with them once including chilhuacles negros and was pleased with it, but it was more than 10 years ago.
As for substitutions, I think well-roasted guajillos are the most commonly offered suggestion, but I don't know how it works out. Given chilhuacles' rarity, I'm surprised Bayless doesn't offer a sub himself?