From reading your other posts on this subject, it sounds to me like you should look for an adult dog instead of a young puppy. That way, you wouldn't have to go through that yucky "puppy stage" and their personalities are pretty much settled in. Labrador Retrievers, even though they are awesome dogs, from my experience, have an extremly long puppy stage. You also said that the dog needs to be small/medium in size. I classify Labs, as well as Goldens, as large dogs, though some can tend to run on the smaller side (like my Golden Retriever, Daisy, for example). Which again, would be why I would recommend getting an adult dog, since you would already know what size the dog would be.

I'm not trying to discourage you in any way, I just don't think a decision like this should be rushed. Just keep visiting your local animal shelter and keep in touch with rescues. You'll find that perfect dog soon enough.