Susan Lanci makes very very small harnesses - like for 1-2 pound dogs. They are pricey but you said you wanted a good one. Doggie Design makes nice harnesses and also the Gooby Freedom harness is nice and comes in a small size. It will all depend on what size your pup is.
I also agree about waiting until the dog is 12 weeks. The thing is, it learns social skills from the mom and litter mates. Things like how rough to play and how to initiate play and not be rude. (Loki is "rude" to other dogs, and that is why - he has has years of training classes but being polite to another dog is not easy to teach like "come" or "fetch" is.) SOME dogs will be have social issue (like being afraid of other dogs or unfamiliar things) if they are taken from mom too early. You might get a dog that will be fine and you might hear about dogs that were fine. But you really won't know until it is too late if that is *your* dog. It's just like kids who aren't ready for kindergarten until they are 6 when others are probably good to go at 4 1/2.
It's not meant to be an insult, it's just that even though many puppies do go home at 8 weeks, 12 weeks is better (even for big dogs which rarely happens). 8 weeks might be OK, but 12 is ALWAYS better. That's all. Good luck with your puppy!