Caponizing = neutering (the animal cannot reproduce afterward.)
De-crowing is a different surgery, more like de-barking a dog. Rumor has it that some vets will do that surgery, but actually finding them appears to be difficult or impossible.
In both cases, the chicken version is more complicated than the dog version, and more dangerous for the animal.
If you want to spend a few hours on the phone, you can just start calling every vet in the area. To save time, start by asking "do you treat chickens." If the answer is "no," you don't have to bother explaining what decrowing is.