Chewie is 11 weeks old and he weight 2 pounds at the moment.
I got him the XS anti-pull mesh harness at wal-mart. It's a little big at the moment but still stays on when I have to go somewhere with him. The harness is padded and looks very comfortable.
I like them because I just slip it over his head and I don't have to deal with the tiny snaps some other harnesses have. I also have one for my 5 lbs toy poodle.
Here is the wal-mart link :
Walmart.com: Yuppie Puppy: Yuppie Puppy: Yuppie Puppy: Yuppie Puppy: Anti Pull Toy Harness, 1 ct: Pets
Unfortunatly you can't see the harness too well but with wal-mart you can always return it if it's not what you like.