I don't own a Thater not an easy brush to source in the UK but I do like the look of the Thater 4125/1 Two Band with the fan shape knot must be a fan as I'm not a fan of bulb shape knots, in fact I've put my new Simpsons M6 up in the trade section looking for one of these brushes.
Try "Shaving i.e." chap called Chris very helpful based in Ireland.