For a reasonable price? The outdoors stores seem to only go down to an 8.
I've got waterproof trousers in a kids' 13 years, which are about a women's 8 (just cheaper), but I really need a 6 in hiking trousers and base-layer bottoms. I'm an 8 on top so that's fine. A kids' 11-12 is too short, it might do for the base-layer, but not for trousers (I'm 5 ft 5). If you're a size 6 where do you buy your gear?