I was unable to find a stand for my curved soprano. So I bought an alto stand and modified it.
I bought an On-Stage Stands double sax stand from musiciansfriend for $30. It's the SXS7201B.
I drilled another hole in the vertical piece, a few inches higher than the other two, for the bottom bell support. Then I used a small grinding bit on a Dremel in a rather weak attempt to make the round hole into a square hole. It's not pretty, but it holds the square-headed bolt just fine.
Next, I narrowed the top bell support, using a vise. I took the end plugs off to expose the small-diameter metal rod inside. The neoprene sleeve is glued together, so I just slid it back a little. I carefully put the two ends of the curved piece into the jaws of a bench vise and carefully closed the jaws a little. I kept measuring the vise opening, and after every half inch I'd undo it and see how it fit the soprano bell.
I decided to use the vise technique on the lower bell support, too, although it probably wasn't necessary.
Now I have a perfect double sax stand for a curved soprano and an alto or tenor. Since I have an on-stage stands single sax stand (an SXS7101B), I can use the interchangeable parts to create various combinations. The stock pieces are adjustable for tenor or alto, but my new custom-bent piece will never fit an alto or larger bell again.
BTW, there's an attachment from on-stage stands that makes it into a Bari stand. It's the SXSA7201B.