I'd go with the pouch around neck method--easily disguised.

We had a client at the vet's office a few years ago who became distraught when she found out her dog wouldn't be allowed to wear his collar, which had on it a St. Francis of Assisi medal, or her rosary, while he was in the kennels and in surgery. I mean, borderline hysterical. But for safety reasons, pets were not allowed to wear "jewelry" (they got fiber paper ID collars). She finally agreed to let the surgery technician keep the items in her pocket while the dog was under, and the recovery technician while the dog was waking up. The dog did fine. Obviously, I have to think he would have done fine, anyway, but it clearly didn't hurt him not to be actually wearing the medal or the cross.