Hello
While I could write pages and pages about finding a responsible breeder, and what "responsible" even means to different people, I'll try to give you a few pointers without writing a novel.
The non-negotiables:
1. Ethical breeders health test. Find someone who can provide you with OFA results for at least both parents (I have OFAs for my puppy's parents and four grandparents). Figure out which other breed specific health tests (CERF, thyroid, cystinuria, cardiac screening are examples) should be done by the breeder before they'd consider breeding a dog.
2. Ethical breeders provide a health guarantee and will want the puppy returned to them if you ever decide to rehome it. Most of them will have you sign a contract indicating that you agree to those terms.
3. Ethical breeders do not release puppies to homes before 8 weeks. The puppies should come with their first set of shots and dewormer already given.
4. Ethical breeders can provide you with references who have purchased puppies from them before.
5. Ethical breeders either choose the puppy FOR you, or limit your choices to a few puppies and allow you to choose out of those. They don't choose which puppy will go to which home until they are 7-8 weeks old. You should be asked to supply your experience, your list of requirements (gender, type of personality you want), and the breeder should help point you towards which couple of puppies fit those criteria.
Negotiables:
1. Showing - it's a prevalent idea that people must show their dogs to be "responsible". I think this is inaccurate. People who breed field line Border Collies or German Shepherds don't show their dogs, they work their dogs. Their dogs are proven through performance of a physical job. People who show their dogs are more likely to health test, research and breed carefully, but that doesn't necessarily mean someone who doesn't show is a BYB (in my opinion).
2. Number of litters from the bitch and on the ground - there are different ideas about how often a bitch can be bred, with some arguing it should be every other year, and some arguing that breeding back-to-back heats and then going several heats without breeding is easier. Talk to breeders about how often they breed and what their reasoning is. Don't buy from someone who breeds a bitch every single year. I'd also be wary of a breeder who has more than two litters a year, or more than one on the ground at a time. There are exceptions, there are accidents, many an ethical breeder has had two litters on the ground at once through extraordinary circumstances, but for the most part, unless they're running a massive breeding operation (which is a whole 'nother bag of worms), they should be producing quality dogs over quantity.
3. Spay/neuter contracts - I would not purchase from someone who asks me to sign a spay/neuter contract, but many breeders do have them. I personally don't want someone telling me I have to spay or neuter my dog, or when that has to be done. But it's not a problem for many puppy buyers.
There are other things to consider, and to ask the breeder about. How does the breeder socialize the puppies? Why did the breeder pick the particular sire? If the breeder doesn't show, what are they doing to "further" or "improve" the breed? Can they speak to the longevity of their lines or which health issues they have seen in their lines?
I'd urge you to not expect to have a puppy home within a few months, especially a DDB puppy. Finding a good breeder can take even longer than your research did. Good breeders most likely don't have unspoken for puppies sitting around waiting for someone to come and buy them - they have waiting lists for their litters and are breeding to satisfy the demand for their dogs. And quite frankly, finding a reputable DDB breeder within 4 hours of you is going to be rough.
DDBSA only has four breeders in the US listed on their website:
DDBSA Dogue de Bordeaux Society of America
This site has a few more:
http://www.dogresources.com/dogue/
This is from the DDBSA website and a fairly good resource which states some of what I have above and goes further in depth:
http://media.wix.com/ugd/8a05dc_ae6daee0758cb0f9ed61ee88c4bb7243.pdf
There seems to be a very good breeder located somewhere near you. Mount Sinai Kennel, who has bred at least one GCH dog, and multiple champions, that I can find. Their website is down, but they are still actively showing. I will PM you their contact info that I found via google search.
Above all, I would suggest being patient and selective. And if you have any questions, or see any red flags from a breeder you have contacted, you should absolutely come back and use this forum as a tool to help you make decisions. There are lots of knowledgeable, experienced puppy buyers here. Good luck in your search!