I have in a past note introduced an interfacing from Staple Sewing Aids - a cotton fusible.  I have since found this to be a much more useful interfacing for reinforcing garment facings than for stabilizing neckties, especially the heavier silk.  Though the HTC "Touch O' Gold II is still my favorite, it is rather expensive.  Fairfield's "Stabilize" is equally effective for most uses and is much more affordable.