The Pfaff Quilt Expression 4.0 has a start/stop button. I have the 2.0 model which does not have s/s button. I love the large harp space for quilting. The 4.0 has been sold for about 5 years now, so there should be some available used, or a year end close out price should be under $1500.
I also have a Brother with start/stop button and speed switch, but it has a very small harp and very little space in the throat, so I would not recommend it for quilting.