Andy, Try Berkshire Products http://www.berkproducts.com/ they may have Butternut and/or Chestnut and they do lots of mail order. So does Hearne Hardwoods. http://www.hearnehardwoods.com/index.html You can also try these guys for butternut, though I’m not sure if they do mail order. http://www.vermontwildwoods.com/lumber.html Google Chestnut lumber and you will get plenty of sellers of reclaimed material. Elm would be a good a substitute, especially English Elm. I would stay away from sycamore unless you’re getting it from someone like Talarico hardwoods, http://www.talaricohardwoods.com/ but be ready to shell out some $$.