
if you contact any of the breed clubs you will be put in touch with reputable breeders. You are right to worry about the source of your pup as this breed is sadly very exploited by puppy farmers, irresponsible and well meaning but lacking in knowledge casual breeders.
Expect a breeder to be really probing as to the lifestyle and type of home you wish to offer as good breeders are understandably protective of their breed and pups :D
If you go on the Kennel Club website, click standards on the right hand bar, tehn terrier, then West Highland, rtead the standard and at the bottom is a list of breed club contacts (sometimes the KC list is a bit outdated, but you should be given current details by the contact listed) :D Good luck!!!!