Answer to: What insurance options, if any, exist to allow an individual to transport valuable items owned by others with minimal liability?

I would suggest Alice and Bob talk to their lawyers. What is needed here may simply be a contract stating that while Bob shall exercise due diligence, Bob is not responsible for any loss or damage while the object is in his care. Note that Alice can still try to sue Bob, but if phrased properly this should prevent such a suit from succeeding unless Alice can show gross negligence or deliberate malfeasance. If Alice wants the object insured while in transit, I think it's Alice's responsibility to find suitable insurance.Note that if Alice was carrying it she might still want to ensure it. Bob isn't the only one who might have an accident. (I carry an umbrella policy that explicitly covers specific equipment that I sometimes travel with and that would be hard to replace. I believe that insurance applies whether the object is in my hands or not. There may be a cheaper way to do it; I presume there are policies specifically for folks like touring artists. Some variant of travel insurance, perhaps. The insurance agent should be able to find something suitable. If not, find another agent.)