There are a few timber frame shops that may stock some curvy, funky wood. I don't have much in hardwood right now. You could check with Collin Beggs in Idaho or Timberhomes LLC in Vermont. Frameworks Timber in Fort Collins could have something as well.

BTW, sections of a (small) circle are really hard to come by, as there's a lot of curvature. More gentle arcs are a lot more prevalent.