There are two consistent sources of dog barking collars available to you.  You can find the collars either online or at a pet store.  Some vets and trainers sell the collars as well, but the majority of owners buy them at the first two locations.

If you purchase a collar at a pet store, make sure you have a long talk with the associate that is helping you out.  A collar has to be right for your animal or the whole exercise is pointless.  The collar should fit snugly without impeding movement or breathing.  The functional unit needs to stay where it belongs, over the voice box even when your pet moves around. 

The weight range for the particular collar should match your dog, and your dog really should not be near the edge of the specified weight range.  An electric collar that is overpowered for your dog will cause unnecessary pain.  One that is too weak will be completely ineffective, causing you to give up in frustration.

If you are purchasing online, then make sure you understand the specs completely.  Look for adjustability, a good return policy and excellent customer service.  Your selection online is usually larger, and you can read reviews on each type of collar by searching the web for a specific model.

A barking collar will only be effective if you work with your dog to control the barking.  No dog should wear a training collar for more than a few hours a day, and they should never be used with anxious or fearful dogs.  Consider your dog’s personality, his needs, and habits when purchasing, and you should do just fine.