I also only use soaps. I recommend a custom Shavemac with a 21mm diameter/45mm loft knot in Finest hair. I consider 14mm to 19mm a small knot, just so you know where I'm coming from. Just email Bernd at Shavemac with the handle style and color, as well as the knot diameter, loft and hair grade you'd like. He'll then set up a personalized web page through which you can order your custom brush. If you go with Finest hair, it will cost as much or less than an off-the-shelf, standard Shavemac, but it will be everything you want it to be. I also think Shavemac's Finest hair grade is as good or better than a lot of Silvertip hair from some makers.
Also see the threads in my signature below. Welcome to B&B!
-Andy