Over the weekend, I was able to receive confirmation that the knots used in Mühle brushes are available by special order. Members are able to obtain nearly any knot from any of their current lines in existing sizes.
According to Christian Müller, General Manager of Mühle: "Requests for special knots are welcome through http://www.muehle-shaving.com/company/contact. However we are limited to the ring sizes 19, 21, 23 and 25. We are unable to experiment with different loft sizes and lengths."
Since there are so many knot types and sizes, pricing will vary by size and material.
This is great news for the shaving community!