The Chihuahua Club of America maintains a list of reputable Chihuahua rescue groups. These groups rescue Chihuahuas of all ages, not just puppies. The only rescue group on the approved list that operates nationwide is called Chihuahua Rescue and Transport.
The other approved, reputable rescue groups on the Chihuahua Club of America's list operate in local areas only, scattered across the United States. Chihuahua Rescue and Transport operates nationwide to find homes for Chihuahuas and Chihuahua mixes. It maintains on-line listings of dogs that are available for adoption. The actual dogs that have been rescued are kept in foster homes until permanent homes can be found.