Found the most comfortable dress pants--where can I find pants with similar material?

I'm skinny, I live in Florida, and I sit at a desk for extended periods, so I like dress pants that are slim and "stretchy" for lack of a better word. I recently bought a navy suit from Banana Republic, and noticed that the material on this particular suit is different from their other suits. The pants are slim, but they are breathable and stretch a bit when I'm sitting. So far, I haven't noticed any permanent stretch in the pants.

The "shell" is 100% wool, but the "lining" is 100% acetate. I assume the acetate is what gives the pants their flexibility, but that's just a guess. Anyway, I was just wondering if anyone knew of a place that sells dress pants that have a similar fit and material to these pants. Thanks!