As you may or may not know, Quebec is infested with puppy mills, where dogs are kept and bred under horrendous and cruel conditions. Pet store puppies come from these places, so stay away from them!
Also walk away from any breeder who uses the words "Tea cup or Toy" to describe their dogs, and any who have not titled their breeders, and do not give guarantees against any genetic defects common to the breed.
If you want a well bred and healthy dog, you may have to wait awhile, travel a good distance, or have one shipped to you.
I know of no REPUTABLE Chi breeder in Quebec. You might want to contact the Chi Club of Canada and ask if they know of any.
Chihuahua Club of Canada
Edna St.Hilaire
2114 Dublin Street
New Westminster, BC V3M 3A9
(604) 521-0922
There is a local rescue who does occasionally have Chis - my sister in law got a 5 lb cutie from them and is thrilled with him. She has 6 cats and no problems with hers.
Animatch
Pit bulls are often excellent with tiny dogs, and I'm assuming you already know that yours is.