I think I would stick with little vest or dress harnesses till she's fully grown. The BB harnesses are not cheap, and would be a waste to buy right now.
My new baby is 17 weeks, and I still use the ferret harness or if she has to wear a sweater, I put one of Cindy's (Chattiesmom) silk harnesses she makes and that is too small for the others on over the sweater. I also bought her a quilted vest harness for the holidays. I will buy her a BB harness, but not till she's finished growning.
