When our old Lab, Maxine, appeared to be approaching the end, I put us on a waiting list with Guiding Eyes for the Blind. The usual wait is something like a year-and-a-half or two years. About 20% of the specially bred dogs wash out as young puppies, (the one we got, Maxine II) was nine weeks old), fewer by far are released as older puppies, and there are very few adult dogs. Labradors, which most of them are, have a _very_ long puppyhood, which is adorable or a huge pain, depending on your disposition. We got Maxine II because Lulu the Inuit dog would be happiest with a Lab, we thought--and she certainly seems to be. Maxine has the makings of an excellent dog, but maturity is many many months away. I wouldn't have taken on the work, except I really like Lulu, and this puppy suits her in ways hardly anything else would have.
P.S. If you don't have time to properly raise and train a puppy, I would first question if you have time for a dog at all. If you feel you do, it might be a good idea to be in touch with shelters, and rescue agencies, and seek a grown dog, already trained. If you have a specific breed in mind, there are often breed-specific rescue and placement organizations. For example, racing greyhounds, retired from the track, are frequently placed in this way, and they tend to work out wonderfully.