We asked our vet regarding bones that would be good for Kate, and we've never had a problem since following her advice...
She gets one or two a week, we buy from a specialty "health dog food" store. But any store that carries the BARF (or any raw diet) should carry them. Kate only gets raw uncooked bones (they are frozen in-store). They have bison, cow, moose - everything you can think of. Kate has done absolutely wonderful with them. We've never had one splinter, she's never gotten the runs - nothing! I'd definitely recommend them, Kate will never get anything else (for bones that is - she still gets dog cookies)! Oh - and they cost around $2 or $3 each, they have different sizes (knuckles, legs, etc)
Another bonus is that it cleans their teeth really well too...