This is a VERY common question. I would have been asking the same thing long ago when I began making dolls. I wasn't on the internet then so I had very limited access to the big world of doll making supplies. I've compiled a list of my main haunts (on the side bar a little ways down). Some may seem a little odd at first. MFasco is where I buy my tubular stockinette for the inner head. Dharma Trading is where I buy the dye for my yarn. J. Hittle is a good place for sewing needles and button craft thread. West Earl Woolen mills doesn't have a website but just 411.com them and you'll find their number. They are a dream to work with. I am buying my yarn for the hair from Henry's Attic and for small amounts, their yarns are available at Catnip Yarns. I love, love, love Bunte Fabrics (but then you already know that). Etsy is a great place to find fabric as well. The bulk of my sewing thread comes from Atlanta Thread and Supply. For tying the head, I use 3/2 Perle cotton and I buy it by the pound from Weaving Works
For most of the closures on the clothing I use Soft Velcro. It is narrower and softer than regular Velcro. I buy that from Joann's Crafts and Fabrics when I have a 40% off coupon.
I really appreciate my suppliers and most of them sell to the general public with out a wholesale account. If you find a new one here that works for you tell them Berrie sent you.