In light of my recent post updating my information about diamond twill wool fabric sources, I figured I should pass on the information I got from Jenn Culler's blog just the other day.
Jenn reported that Stas Volobuev, who is based in Kursk, Russia, is selling undyed broken diamond wool twill (as well as other fabrics) for 30 Euros per meter plus shipping. The thread count of Stas's diamond twill is 36 x 16 per cm, and thus is quite fine (and an unbalanced weave, as was true of many of surviving period fabrics). The cloth is 158 cm (about 62 inches) wide, which makes 30 Euros a very good price (though shipping from Russia is likely to be substantial).
You can contact Stas to arrange a purchase at his Facebook page, here. His Facebook page says that discounts for "natural dyes are available if you buy them together with cloth proportionally". That may be worth exploring if you would prefer dyed diamond twill for your project.