Even if she is small I still think you should walk her. Dogs are happier and healthier if they get exercised. You can buy small harnesses, I don't see the problem. Get two ID tags one for the harness one for the collar. Use the collar when you are indoors. I've seen a 1 lb Chihuahua puppy while volunteering at the vets and even she had a collar. I don't see how it would hurt them...
I use Aspen harnesses but I don't think it would get small enough for your dog. I have a harness made by "TUFF" and it can fit really small dogs. I like Red Dingo ID tags:
Stainless Steel with Enamel
Just go to your pet store and pick one out that you like.