To make your own, download a pdf of the book, Make a Ray Jacobs Rocky Mountain Dulcimer, here. The paper version is on sale through the HP bookstore.
My brother went to the Farm & Wilderness Camps in Vermont when he was a kid. Now his daughter is the camper, he helps out teaching woodwork. I sent him the dulcimer book, and he helped about a dozen musicians make their own instruments, not just campers, but counselors as well. I hope the idea will get passed around. The sound is so good, and they’re so easy to make. If you like it, please do share the download freely — it’s published under a creative commons license to support sharing.