Here's a link of where I buy my Cosequin.
Cosequin Regular Strength (90 capsules)
I don't know if you can give it to pups that young though, ask your vet.
Also you can search this forum "luxating patella" and you will get a wealth of information. Some members have had the surgery, some elected not to. Depending on what grade your pup has, you may want to limit jumping and stuff. Well you should limit jumping for yorkies anyway, but some of them you just can't stop them! LOL
BTW Welcome to YT! What's your pup's name?