Hi Kay, What your looking for is called a "restraining collar" . You can either buy one from your vet, or do a Google search. You can start by visiting kvvet.com, click on' pets', than click on 'Training and restraints', than look for restraining collars.
It's a good as place as any, for you to start. There are a lot of different pet catalog companies, with a variety of restraining collar styles.