I presume you mean bones made from wood. "Most" bones, since their mid 19th century heyday were, generally, made from wood, apparently to replace those from the skeleton.
Percy Danforth's book (check Elderly Music) has measurments. Otherwise, pick up a set and trace them. The easiest way is to rough them out on a bandsaw and then shape and finish on a belt sander.
Many make bones from rib cages. I find them less than satisfactory but servicable in a pinch. I understand that the real "good" skeletal bones are from the shin. These I have not yet attempted to reproduce but I have purchased a set (Lark in the Morning) which I suspect to be such. Either way you should boil them up to remove fatty deposits and that will help them to dry. Sources are the Butcher or a local Slaughterhouse.
Also check www.rythmmbones.com