Most of the pet stores have bleached bones, without the stuffing. You can get some pretty good sized ones too. I used to do a lot of bone carving, and used to go out in the dairy pastures, and get the bones of the cows that died. I would boil them, and then bleach them for a day, and and saw them in half, and then carve them. The will polish up really nice, almost look like ivory, or plastic. I have not noticed any difference from the raw bone, or dried bone, or boiled bone. Once it dried, it was the same as the others, as far as I could tell, from a carving point. I used to buy leg shanks till they got as expensive as the pricier cuts of meats. I would cut the meat off for stew, and use the bone for the marrow, in the stew, and then clean off the bone, and carve it. I would select the thickest shank bone for that. Also those big raw hide chew bones, when soaked, will untie, and make good practice pieces for brain tanning.
Usually there are a couple of pieces in there, of various sizes.
If you use a grinder of any sort, wear glasses, and a dust mask.
Good luck.
Wayne