A few weeks ago, I ordered some diamond-twill samples from Handelsgillet in Sweden. They arrived this morning.
Handelsgillet represents that their wools are all 100% wool, and, judging from the feel of these samples, I believe them. They are light, and soft, but not too thin, and of a "medium" thread count. The image of them that appears with this post is a direct scan of the samples, not a photograph. The price is 295 SEK per meter (about $41 USD), which, though steep, is not impossible for the 2 or so meters I'd need for an apron dress. The colors are muted, as you can see, but the blue is a nice shade.
If only they weren't two-toned, I would definitely start saving up for a couple of meters of the blue. As it is, I will probably think some more about what diamond twill to order, and from whom.