Contracts

if the client wants to contact me in the future, I simply tell them that due to a breach in contract on their part, I am not interested. <<

have you really thought this thru. you are upset that you lost a client who provided free material. but you would refuse to take that client back if they offered you more free material. do you make a habit of refusing free money? i would not turn down free material simply because i had been left out of a couple transactions.
i don't see what kind of contract you could write. you do not generate the material. you do not provide any containers. you are not paying for the material. basically you do not provide any type of service.
i am confused over what you are trying to accomplish. you can not force anyone to deal with you. sounds like you need to offer them something that makes them want to deal with you and only you.