There is not a simple answer to this question, because, quite frankly, it depends on which clothing and accessories you are wanting. My seamstress and I make almost all of the clothing that I sell (we do not make the sweaters) and we make them to fit the bears that I use. So, if you are trying to fit my teddy bear clothes on a very different size of bear, it is not going to work. Also, many of my clothes are not made to take off the bear and are sewn closed, rather than buttoned, or snapped, etc. But, if you are wanting a wrestling singlet, or a swimsuit, those are made of a very stretchy knit and could be adapted to another size of bear. The stretchy fabric would allow some variance in size and still fit nicely.
Accessories are another matter. Most of the accessories that I use are purchased for my bears. I do what I can with the sizes of the accessories, but usually there are not alot of choices. I attach many of the accessories with hot glue or a few stitches, so if you buy them separately, there may not be a way for your bear to "hold" the accessory you are wanting. If you understand that the accessories you want may not fit your bear, or may not be the right size to look good with your bear, then you can buy them from me.
In summary, I am not opposed to selling clothing or accessories without the bears. But, I cannot guarantee a good fit, and I can't guarantee that the accessories will work for you either. I am not interested in selling you something that you won't be happy with in the end, so I try to explain everything up front. It's always best to contact me first if you wanting something for your own bear. Communication from the beginning is really best way to go.