There won't be one. In England coats of arms are granted to individual men and are inherited by individual men, not families. Now when a man was granted a coat of arms all sons obtained one with some differences. Only the oldest son inherits his father's upon his father's death. The surname product business is a racket. In the U. S., for instance, we have no laws regarding heraldry and a person can display any coat of arms they wish but to do so is considered usurpation of another's identity and in bad taste.
I don't know if you are male or female, but if you, your father or your husband is entitled to a coat of arms, you would have to trace your ancestry back to the person to whom the arms were originally granted. Frequently more than one man with the same surname, not all necessarily related, were each granted their own coat of arms, all different.
No one peddler who sells them on the internet, at shopping malls, in airports,in magazines etc will have all of them. They don't need to in order to sell to suckers. The only time they will have more than one coat of arms associated with the same surname is if more than one man with the same surname from different national origins were granted one. Then they will have one of each and there might have been 50 others. Most men with that same surname are not entitled to a coat of arms at all as they do not have any direct male line ancestor that was ever granted a coat of arms.
Now you might have several in your family tree. That doesn't mean you are entitled to any one of them. It just means that after doing research of your family history and you find more than one ancestor that were granted a coat of arms and if you have a book printed or even published on your family history, it is valid for you to put pictures of your ancestors' coats of arms in your book. However, it would not be valid to put pictures in your book of those that were granted to men with the same surname as your ancestors.
If you are an American and you have any English lines that goes back to early colonial days in the American South you have an excellent chance of finding several in your family tree. In that case you probably have some cousins, perhaps you never met, that have the ones the ancestors you share in common with them brought over from England 350-400 years ago. As a rule they don't display them.
They aren't any good for buying groceries or gasoline. They don't have their 401k.
Any time you go into someone's home and see one of those walnut plaques on their den wall or over their fireplace just smile to yourself. Chances are they really think it belongs to them and it would be rude to laugh at people in their own homes about something like that. A coat of arms that has been legitimately passed down from father to son will not be mounted on a walnut plaque and will not have a surname over or under it. Most were granted before people had surnames.
Now you can have your own designed and registered with the American Heraldry Society. However, since we don't have laws regarding heraldry there is nothing you can do to stop someone else using your coat of arms.
http://www.college-of-arms.gov.uk/Faq.htm
They grant coats of arms for England and Wales
http://americanheraldry.org/
If you are an American you might contact these people. They can help you if you give them your family tree to see if you are entitled to a coat of arms.