Brought my girl to my daughter's where her two dogs had a yak milk bone. My Gia spent several 30-40 minute sessions with it.
Found one when I got home. Nope.
Tried yak cheese bone. Again, nope.
Got a marrow bone, which she loved, but one, it's messy, and two, left it outside one night to find it filled with ants in the morning.
Last attempt. - cruelty free - important to me!
split elk antler. Several sessions with it, and it's still going.