Sometimes suppliers have unusual stock blanks. I've seen chestnut, sycamore, and a couple others. If you try to find lumber thick enough and sized right for stocks you'll do a lot of looking and probably paying too. There are good reasons why maple, walnut, and cherry are the most common stock woods. They are relatively common, grow large enough to be worthwhile to saw into gunstock blanks, have good dimensional stability, adequate hardness and strength and dent resistance, and are workable and attractive.