http://www.cavalierhealth.org/Cardiologists.htm
The link above is a list of Cardiologists just click on your State to find one in your area.
I would call and speak to them, I have had to do this before, I called several while I was dealing with two Cavaliers with heart issues.
Prehaps you can get your vet to speak with them.
I just cannot imagine the vet not referring you to a Cardiologists if he thought it was more than an innocent murmur. Because he obviously realizes you are thinking of taking legal actions and he would not want to be thought of as also being neglectul for not referring you to a Cardiologist.
Deana
Prestigeous yorkies